A questionnaire was sent to the 1994 membership of the American Medical Society for Sports Medicine to describe attitudes regarding allowance of sports participation for athletes with a single kidney. Using a hypothetical scenario of a high school or collegiate preparticipation examination, the respondents were asked if they would preclude or allow participation in collision and contact sports for an athlete with a single kidney. Of 438 respondents, 237 (54.1%) indicated that they would allow full participation in sports after discussion of the possible risks. The percentage decreased to 41.6% if the athlete was their son or daughter. These results indicate that the decision to allow participation in this situation remains controversial, but they also provide some support for those physicians who allow participation.