A previous study undertaken by this department showed follow-up to be of little value in tracing curable recurrences in patients with colorectal cancer who had curative operations. The aim of the present investigation was to determine if more intensified follow-up would result in earlier diagnosis of recurrences and thus lead to earlier and more effective treatment. Altogether 599 patients with colorectal cancer were treated between 1973 and 1977. The 363 (61 per cent) patients who were operated upon for cure entered the study and were followed up until December 1979. The same incidence of recurrence was seen in both series, but, with the more detailed protocol, they were more frequently detected before symptoms developed. However, the rate of curative reoperation for recurrence was not changed and only few patients survived after such reoperations. The conclusion is that the previous protocol is as efficient as the detailed one while no effective treatment of disseminated disease exists.