In briefA case-control study was under-taken to study risk factors for collapse in nonelite runners who completed a marathon. Information was gathered on all runners who showed signs of collapse at the finish line and were treated in the medical unit, and on controls matched for finishing time. Runners who collapsed were compared with all finishers as well as with the controls. Significant factors associated with collapse were higher running speed (relative risk ratio = 5.24) and previous heat injury (p =.034). Differences in gender, age, marathon experience, current illness, fluid intake, and effort were not significant.