Blood donors' motivations and reasons for lapsing and never donating were determined from a questionnaire completed by 489 adults (89 regular donors, 105 lapsed donors, 295 never donors) in Leeds, UK. The free text responses were classified according to themes that arose. Altruistic motivations including reciprocation and kinship towards family, friends, and unknowns were most numerous. Other motivations related to the NHS or National Blood Service, obligation, occupation, self-interest, convenience, peer-influence, health benefits, a rare blood group, donations being useful, a TV programme, or ethnicity. Reasons for non-donation were personal, medical, donation centre- or procedure-related, exclusions, and age-related. Suggestions are offered to increase the blood supply.