This retrospective study was aimed to characterize the diagnostic process of cancer with respect to level of care, initial symptoms, and diagnostic procedures. It was based on analysis of medical records of all subjects with colorectal, pulmonary, breast or prostate cancer, reported to the Swedish Cancer Registry during defined periods of time in the community of Kungsbacka with about 46,500 inhabitants. Initial symptoms, diagnostic procedures, outcome of diagnostic procedures, level of care, and doctor's delay were analyzed. Most patients (62-73% for the different cancers studied) first visited a general practitioner for the symptoms which lead to the diagnosis of cancer. The most common initial symptom for colorectal cancer was defecation abnormality, for breast cancer a palpable mass in the breast, for pulmonary cancer cough, and for prostate cancer symptoms of prostatism. There was no difference in doctor's delay between general practitioners and other physicians. Nonspecific blood laboratory tests made little contribution to the diagnosis of cancer. The results indicate that most cancers of the types studied are diagnosed in primary health care and that it is possible to improve the identification of the few malignant cases among the "noise" of benign diseases, both with respect to accuracy and cost-effectiveness. It seems that focused investigations such as fecal occult blood tests and rectoscopy should be more frequently used in patients with gastrointestinal symptoms.