Ninety-nine physicians participating in a Nordic multicenter trial on myeloma in 1990-1994 were surveyed, by means of a mailed questionnaire, with respect to their attitudes toward clinical trials and their opinions regarding the importance of certain factors influencing patient accrual. The inclusion rate of each participating clinic was recorded. Questions related to attitudes of presumed importance for patient accrual were analyzed for associations between the response distribution and the inclusion rate for the corresponding clinics. Ninety-three of the surveyed physicians responded to the questionnaire. The survey indicated that the physicians considered the scientific purpose of a trial to be the most important factor for patient accrual, followed by the simplicity of study protocol, the rightness of ethical aspects, the quality of communication with the study organization, and the degree of participation in investigators' meetings. A positive correlation to patient accrual was found for several attitudes held by the participating physicians, including their perception of the importance of a quality-of-life study in the protocol, their conception of the simplicity of the study protocol, their frequency of participation in investigators' meetings, and their awareness of cost and reimbursement levels for entered patients.