BACKGROUND: It is often claimed that a regulated kidney market would significantly reduce the kidney shortage, thus saving or improving many lives. Data are lacking, however, on how many people would consider selling a kidney in such a market. METHODS: A survey instrument, developed to assess behavioural dispositions to and attitudes about a hypothetical regulated kidney market, was given to Swiss third-year medical students. RESULTS: Respondents' (n = 178) median age was 23 years. Their socioeconomic status was high or middle (94.6%). 48 (27%) considered selling a kidney in a regulated kidney market, of whom 31 (66%) would sell only to overcome a particularly difficult financial situation. High social status and male gender was the strongest predictor of a disposition to sell. 32 of all respondents (18%) supported legalising a regulated kidney market. This attitude was not associated with a disposition to sell a kidney. 5 respondents (2.8%) endorsed a market and considered providing a kidney to a stranger if and only if paid. 4 of those 5 would sell only under financial duress. CONCLUSIONS: Current understanding of a regulated kidney market is insufficient. It is unclear whether a regulated market would result in a net gain of kidneys. Most possible kidney vendors would only sell in a particularly difficult financial situation, raising concerns about the validity of consent and inequities in the provision of organs. Further empirical and normative analysis of these issues is required. Any calls to implement and evaluate a regulated kidney market in pilot studies are therefore premature.