Colorectal cancer is the second main cause of cancer death in Germany, although several measures related to primary prevention are described, and the utilisation of existing diagnostic tools (faecal occult blood test = FOBT, colonoscopy) is known to significantly decrease incidence and mortality. However, screening rates remain low in Germany, and insufficient knowledge of prevention possibilities is assumed to be responsible. The aim of this study was to investigate the knowledge related to colorectal cancer prevention in a Bavarian population, in the context of a regional public awareness campaign ("Active against Colorectal Cancer"). 618 individuals between 50 and 90 ys of age participated in a telephone survey (m: 219, f: 399, 63.2 +/- 9.17 ys); the participants were inhabitants of two Bavarian districts. The questionnaire consisted of open-ended questions concerning preventive behaviour, colorectal cancer screening, risk factors, early warning signs and knowledge of colorectal cancer information. More than 80% of participants recalled healthy diet as a possible protective factor against colorectal cancer; a distinctly smaller percentage, however, could correctly define concrete dietary factors: e. g., fruit and vegetables were named by 54.5%. 66% of participants knew that unusual rectal bleeding might be a warning sign of cancer. Colonoscopy was the screening test that was most frequently recalled (61.5%); fewer participants named FOBT (32.8%) and rectal examination (11.5%). The results demonstrate that for many knowledge items, females proved to be significantly better informed than males. The most frequent sources of colorectal cancer information were newspapers, magazines, television and/or radio (named by 76.7%), as well as physicians and pharmacies (45.1%). 11.5% of participants attended the regional public awareness campaign "Action against colorectal cancer"; this subgroup had a better knowledge of some aspects related to colorectal cancer prevention. Evidently, the interviewed Bavarian population of 50 years or older lack knowledge of risk or protection factors for colorectal cancer. Knowledge of existing screening tests was also poor. These findings can serve as starting point for information campaigns tailored for target groups.