Patients express concerns about the safety of donated blood. Do they have similar concerns about potential 'blood substitutes' and does the way information is presented on these options alter patients' perceptions? A two (informational frame: gain or loss) by four (transfusion type: human donor blood, human haemoglobin, bovine haemoglobin or perfluorocarbon emulsion substitutes) by three (patient group: adult haemophiliac/leukaemia patients, relatives/friends of haemophiliac/leukaemia patients and controls) between-subjects design was used. There were 82 patients, 118 relatives/friends and 263 controls from the UK. Blood substitutes were perceived as being significantly less safe than donor blood. Perceptions of safety were greater when transfusion information (regardless of transfusion type or patient group) was presented as gains rather than losses. Different demographic and psychological factors predicted perceived safety (e.g. sex) and perceived risk (e.g. age and experience).