Recruitment of living donors represents a medical and moral responsibility. Their motives are often complex. Categories of motives and factors causing concern were identified from a previous in-depth interview study and from the literature. The aim of the present study was to evaluate these motives. A questionnaire was sent to 207 potential kidney donors undergoing evaluation for donation in Norway and Sweden. They were asked to mark on a visual analogue scale, 0-10, the importance given to each of nine motives and five factors of concern. Questions were also asked about who took the initiative and the source of information. The response rate was 74%; 154 questionnaires were returned. The strongest motives to become a donor were a wish to help (median 9.3), self-benefit from the recipient's improved health (median 9.2) and identification with the recipient (median 9.1). In contrast, a sense of guilt regarding past relationships (median 0.9), pressure from others (median 0.8), a religious motive (median 0.8) and increased self-esteem (median 0.7) were rare or weak incentives for donation. There were large individual variations in the mix, particularly regarding moral duty (5.6, range 0.1-10.0). Most potential donors (64%) had taken the initiative for the assessment themselves, but in 22% it was the recipient's physician. Physicians were the dominant source of information. The potential donors expressed much more concern for the recipient than for themselves. Living kidney donor assessment includes an exploration of the individuals' mixed feelings. An analysis of the motive enables individualized treatment and support for non-donors.