Swimming at the 2004 Summer Paralympics, in the Olympic Aquatic Centre was competed in freestyle, backstroke and butterfly (classes Sn), the breaststroke (classes SBn) and individual medley (classes SMn).
Swimmers with a physical disability were assessed on muscle strength and the scope and coordination of movement, and their impact on different swimming styles. The resultant classes were (lower numbers corresponding to more severe disability):S1-S10 for freestyle, backstroke, and butterflySB2-SB9 for breaststrokeSM3-SM10 for the individual medleySwimmers with vision impairment, depending on the degree of vision loss, were classified as S11 (worst vision loss), S12, or S13 (least)
