Abstract Chemical faecal occult blood testing has been proposed as a means of screening for colorectal cancer (C.C.) in populations or in identified high-risk groups. The level of public participation is a critical factor in the effectiveness of screening programmes. This study was conducted as a methodological pretest for an intended investigation of factors influencing screening participation. Faecal occult blood screening was offered to 728 employees of a teaching hospital in Sydney, New South Wales and 41% participation was obtained. Both participants and non-participants were questioned on demographic and social background factors, on their experience of C.C. in others, and on their reasons for participating or not participating. Major reasons for participation were: a general feeling of the importance of health checks and screening tests; a belief that it is important to diagnose C.C. early; and the fact that the test was simple and easy to do. Prominent self-acknowledged reasons for non-participation were indifference, procrastination, absence of previous bowel complaints, preference for one's own doctor to do such tests and inconvinience or lack of time. Those more likely to participate were: females; those of Australian or British origin; single, separated or divorced persons; those having two or more dependents and those with personal knowledge of a C.C. patient.