The aim of this study was to describe some of the factors that might play a role in influencing attitude to xenotransplantation: first, the consideration of receiving cells and tissue from xenotransplants in relation to whole xeno-organs; secondly, the fact that there is greater uncertainty regarding the result and risk of infection associated with xenotransplantation than with allotransplantation. We also describe the attitude to research on xenotransplantation, and the relationship between the attitude to receiving a xenotransplant and an allotransplant. Finally, we describe the attitude to xenotransplantation in relation to treatment for renal failure and waiting-time for allotransplantation. A questionnaire was sent to randomly selected members of the public aged 18 to 75 (n=1,000) and to all patients in the same age range who were waiting for kidney transplants in Sweden in the spring of 1998 (n=460). The response rate was 60% among the public and 87% among the patients. Both study groups were positive to a greater extent in their attitude to receiving cells and tissue than to receiving a whole organ such as a kidney. The response 'rather positive' to receiving organs was generally favored by the public, whereas the most generally favored response to receiving cells and tissue was 'very positive'. When there was suggested to be a greater uncertainty regarding the outcome with xenotransplantation compared with allotransplantation, the number of negative and uncertain respondents increased, both among the public and the patients. Eighty percent of the public and about 90% of the patients were in favor of continued research on xenotransplantation. Of those members of the public who responded, the attitude to receiving an organ from a human was positive in 86% of cases, with an emphasis on 'very positive'. There was a moderate relation between the attitude to receiving an organ from a human and to receiving a xenotransplant. Among the patients, there was no systematic or strong relation between the attitude to xenotransplantation and the kind of dialysis treatment they were on. Neither was there any systematic or strong relation to the waiting-time. The overall impression is that the attitude to xenotransplantation seems to be most influenced by whether the xenotransplant would involve whole organs or cells and uncertainty regarding the outcome.