First of all, the list of ailments.

Burn is a serious ailment that reduces your Pokémon's Attack stat by 1/2. It also causes your Pokémon to lose a set amount of HP every turn; in RBY, 1/16th of your total Health. In GSC, it is 1/8th.

Burn is inflicted by most Fire attacks, with a 9.8% chance. However, in Pokémon Stadium, Fire Blast has a 29.7% Burn rate. Houou's trademark attack Sacred Fire has a 49.6% chance of Burning. Fire Spin does not Burn Pokémon.

Freeze can render a Pokémon useless until it is cured; in link battles, where items are not allowed, this usually means the Pokémon is finished. Freeze does not affect stats or do damage, but it prevents the Pokémon from making attacks. Only two moves may be used by Frozen Pokémon; Flame Wheel and Sacred Fire. These moves will cause the Ice to melt. The Freeze status can also be removed by allowing your opponent to strike the Frozen Pokémon with a Fire attack. (Obviously, you would have to trick him or her into doing that for you.) In Gold and Silver, Freeze is just like Sleep in that it wears off after 1 to 8 turns.

Freeze is caused by most Ice attacks, with a 9.8% chance. Icy Wind does not Freeze.

Paralysis is the most popular and debilitating ailment in use. Paralysis has two effects; one, the Pokémon's Speed is cut to a quarter of its original value. Two, the Pokémon has a 25% chance of being 'fully paralyzed', meaning it misses a turn.

Paralysis is inflicted not only by Electric attacks, but by many other types of attacks as well. All Electric attacks can Paralyze; most with a 9.8% chance. Thunder and Spark have a 29.7% chance and Zap Cannon is guaranteed (if it hits, that is). Thunder has a 9.8% chance of Paralysis in Pokémon Stadium 2. Thunderwave, Stun Spore and Glare do no damage, but they are guaranteed to Paralyze. Other attacks that have 29.7% Paralysis rates include Lick, Body Slam and Dragonbreath.

In addition, Tri Attack has a 19.9% chance of either Burning, Freezing or Paralyzing the opponent.

Sleep is a very dangerous ailment that has been restricted in official battles. Official tournaments, as well as many trainers, use the 'Sleep Clause'- only one Pokémon may be put to Sleep at a time. That Pokémon must awaken or faint before another can be put to sleep, otherwise the opponent loses by default. Sleep can last from 1 to 8 turns, during which time, your Pokémon cannot attack. The only moves it can use are Sleep Talk and Snore. In addition, the moves Dream Eater and Nightmare can only be used on Sleeping Pokémon.

Pokémon can be put to Sleep only by a small handful of moves. Spore is the best Sleep move, with 99.6% accuracy. Sleep Powder and Lovely Kiss are right behind with 74.6%. Hypnosis has only 59.6% accuracy, and Sing is the worst with 54.7%. None of these are direct-damage attacks.

Poison is the classic Health-lowering technique that has been refined into a science over the years. Poisoned Pokémon lose 1/8th their max Health each turn (1/16th in RBY) and also take a point of damage every four steps out of battle. Toxic can inflict 'bad poison' which starts at 1/16th in all versions, but the damage done doubles as time wears on. Switching, however, will cause it to revert to normal Poison.

Confusion is not considered a 'major' ailment because it does not change your status, thus, your Pokémon can be Confused as well as Burnt, Paralyzed, etc. Once Confused, your Pokémon has a 50% chance of hitting itself. No matter what the attack (even if a damaging attack was not chosen), if your Pokémon hits itself, it does it with a 40 power Physical attack that takes no particular element. It does not Critical Hit. Confusion lasts from one to four turns.

Confusion is second only to Paralysis as the most irritating ailment, and God help the sucker who gets hit with both at the same time. While switching can remove Confusion, you're still giving your opponent a free hit. Confusion is inflicted by Confuse Ray (99.6%), Swagger (89.5%), Sweet Kiss (74.6%), and Supersonic (54.6%). Damaging moves that carry Confusion sideaffects include Confusion and PSY Beam (9.8%), Dizzy Punch (19.9%, GSC only), and Dynamicpunch (guaranteed, if it hits). In addition, Petal Dance, Thrash and Outrage will Confuse the user for one turn after they have run their course. Equipping a Pokémon with the Berserk Gene will cause it to be permanently Confused in GB GSC, but on Pokémon Stadium 2, the confusion will wear off in 1 to 4 turns.

Safeguard is the optimal ailment-preventing technique. It does not heal them, but for five turns (including the turn used), your entire Pokémon team is shielded from all status ailments, including Confusion.

Substitute can protect the user from all Status effects until it breaks. It can also be passed to other Pokémon with Baton Pass.

Heal Bell is a very rare technique that can cure your entire team of Burn, Freeze, Paralyze, Sleep and Poison. It cannot cure the user of Sleep, however (through the use of Sleep Talk). It does not affect Confusion.

Rest can cure the using Pokémon of Burn, Paralyze and Poison. It has to be used to work, so obviously, Frozen or Sleeping Pokémon cannot use it. In addition, the using Pokémon falls asleep for three turns.

Haze removes ailments in RBY, but has no effect on status in GSC. Nor does it affect Burn or Paralyze's Attack or Speed cuts.

Sunny Day will prevent Pokémon from Freezing.

Rain Dance will prevent Pokémon from thawing out.

Items like Burn Heal, Antidote, the Poké Flute, and Full Heal can be used to cure major ailments in-game. None of these can be used in link battles, however.

A Pokémon cannot have more than one major status ailment at a time. If a Pokémon is Burned, it will never Freeze. A Sleeping Pokémon cannot be Paralyzed. However, Confusion is not a major ailment, so it can be used if another ailment is already in place.

Poison Pokémon cannot become Poisoned themselves. As well, Grass Pokémon cannot be hit with Leech Seed. All other types of Pokémon are fair game, and do not discriminate- a Fire Pokémon Freezes just as often as an Ice Pokémon does. However, if an element is completely ineffective against another element, it may not work- Steel Pokémon cannot become Poisoned through Toxic or the like (but Twineedle can Poison them). Ground types will never be affected by Thunderwave. Mud-Slap or Sand-Attack do not work on Flying types. However, for some reason, Normal and Ghost status attacks work on each other. (Confuse Ray, Sing, etc.)