Endoscopic removal of colorectal adenomas reduces the incidence and mortality of colorectal cancer (CRC), but follow-up surveillance is recommended. Compliance with the Dutch surveillance guidelines and detection of neoplasia during follow-up has been evaluated in daily practice. From 1987 to 1996, 383 consecutive patients with colorectal adenomas (56.4% male, 61.8+/-11.3 years) were included and followed until December 2000. The mean follow-up was 80.5+/-42.5 months with 2.2+/-0.9 follow-up endoscopies. A total of 32.5 and 27.3% of follow-up endoscopies were performed >25% (time between advised and actual endoscopy) too late or too early, respectively. At the end of follow-up, 33.4% of patients had left the follow-up (two-thirds died) and 60.1% were known with co-morbidity. A first, second, third, fourth and fifth follow-up endoscopy had been performed in 327, 238, 132, 64 and 35 patients, respectively. Adenomatous polyps (with high-risk polyps) were detected in 100% (42.6%) of the index endoscopies and in 25.1% (17.4%), 23.9% (10.5%), 28.0% (12.1%), 34.4% (25.0%) and 37.1% (17.1%) of the first to fifth follow-up endoscopy, respectively. CRC was diagnosed in seven patients (46.1+/-22.9 months after index endoscopy), resulting in a standardized incidence ratio of 1.4 (confidence interval 0.6-3.0, P=0.4) compared to the general population. In this daily practice, high numbers of total and high-risk adenomatous polyps were found during follow-up surveillance. The incidence of CRC was not significantly different from the general population, which might be due to the intensive follow-up and removal of polyps. These findings support the importance of follow-up surveillance. However, the high overall morbidity and mortality should be taken into account when selecting patients for an intensive follow-up programme.