Objective: to analyse the association between rectal bleeding or a family history of colorectal cancer (CRC) and the results obtained in two rounds of a CRC screening pilot programme performed in L'Hospitalet, Barcelona, Spain. Subjects: males and females (50-69 years) were the target population. Together with the invitation letter, they received a questionnaire in which they were asked about rectal bleeding, family history of CRC and related neoplasms. The screening test was a guaiac-based faecal occult blood test (FOBT), and colonoscopy for positive tests. Results: 25,829 FOBT were performed in 18,405 individuals. Information on rectal bleeding and a family history of CRC were obtained for 9,849 and 9,865 cases, respectively. Male sex (OR = 1.32), 60-69 years of age (OR = 1.48), rectal bleeding (OR = 1.84) and history of CRC (OR = 1.54) were independent predictors of positive FOBT. With regard to colonoscopy, a greater risk of diagnosing advanced neoplasm was observed among men (OR = 2.47) and subjects with a family history of CRC (OR = 1.98). Conclusions: CRC screening programmes must have instruments that make it possible to select the candidate population and the possibility of offering a study suited to the risk of individuals who are not susceptible to population screening by means of FOBT.