Extensive study has been done on male subjects dealing with gait analysis, but similar investigations of women runners are limited. The purpose of this study was to quantify the essential characteristics and alterations in gait mechanics of women marathoners. Forty elite women marathoners were filmed at four camera locations during the first U.S. Olympic Women's Marathon Trial. Data were quantified with a microcomputer and digitizing system. Quantification of 11 kinematic and temporal variables of gait were obtained. Five variables were examined bilaterally to determine degree of symmetry. Results showed remarkably consistent characteristics of gait across the four camera locations. However, substantial changes did occur between the third and fourth camera locations in stride length and horizontal velocity. All subjects displayed little asymmetry throughout the race. Minimal differences between the top and bottom 10 finishers were noted. There are differences between the gait patterns of men and women distance runners. Stride length, support/nonsupport time ratio, and percent overstride appear to be important factors for success of women distance runners. Most alterations in gait mechanics appear to occur between the 20- and 24-mile marks of the marathon.