OBJECTIVE: To study the occurrence of symptoms related to the five most common forms of cancer among patients regularly visiting primary care. To estimate the proportion of symptoms needing GP examination, and the number of tumours thus diagnosed. DESIGN: Patients with some form of non-malignant chronic disease received a letter with information about cancer-related symptoms along with an invitation to regular check-up. The letter described the most common symptoms of breast, colorectal, lung, prostate and skin cancers. SETTING: 12 health centres in Kalmar County, Sweden. SUBJECTS: 5200 patients aged over 40 years. RESULTS: One patient in 13 reported cancer-related symptoms to the GP. Women reported more symptoms than men, and almost half of them had had symptoms at previous check-ups. The GP was able to explain 7 out of 10 patients' symptoms directly. When other symptoms were examined, 8 cancers were diagnosed as well as 6 pre-malignant tumours, corresponding to 3 tumour diagnoses per 1000 check-ups. CONCLUSION: While attending regular check-ups, patients may not report symptoms which cause anxiety and sometimes indicate serious diseases. It is possible to widen the perspective and link both primary and secondary prevention of certain cancers to the check-up.