The ability of the blood transfusion service to promote cancer screening using the uptake of colorectal cancer screening offered to blood donors as a model was measured. Blood donors were sent an explanation of colorectal cancer screening with their appointment time to give blood. Free faecal occult blood tests (Haemoccult) were offered by a doctor to donors who attended the Leicester Blood Donor Centre. 556 registered blood donors (309 men, 247 women) aged 51 to 65 years were invited to donate blood over a three month period. Of the subjects who arrived to donate and accepted screening. 63% completed a faecal occult blood test with similar compliance in men and women (66% vs. 59%, chi 2 = 1.0, ns). Compliance was higher in older donors aged 61 to 65 years than those aged 51 to 60 years in both men (90% vs. 60%, chi 2 = 7.0, P < 0.01) and women (87% vs. 51%, chi 2 = 6.2, P < 0.02). The proportion of the total target population screened, which included those donors invited to give blood but who did not attend was 21%. This approach successfully targeted donors who attended to give blood, although only a small proportion of the total target population was screened. Blood donor centres could display cancer screening and health promotion literature and encourage doctors supervising sessions to provide further information and advice to donors.