Psychiatric assessment of potential volunteers for hazardous biomedical experimentation should include an assessment of the motivations underlying the altruistic action of volunteering. Screening goals include evaluation of informed consent as well as screening out experimental subjects who would be likely to be psychologically harmed by participation. This discussion of psychological issues to be considered, beyond those of informed consent and screening for severe psychopathology, originated in the psychiatric screening of the small group of original volunteers for the "Dobelle eye" Artificial Vision Project. These individuals entered the project over 20 years ago at a time when they could expect no tangible benefit from participation. Superficially altruistic behavior, such as volunteering for this project, serves multiple psychological functions and in a given clinical case, the determinants are often complex. A spectrum of altruistic behavior is suggested, based on interviews with these original subjects as well as from extensive evaluation of patients studied in the setting of psychoanalytic treatment with one of the authors (B.J.S.). We suggest that adaptive altruism can explain the finding that some volunteers gained actual psychological benefit from their participation. This unanticipated finding, that participating in research as an experimental subject can result in lasting improvement in self-esteem, is discussed. Suggestions are made for increasing the likelihood of such benefit. Ethical ramifications are addressed.