A series of 1019 patients with small cell carcinoma of the lung, treated at the Department of Radiotherapy and Oncology at the Helsinki University Central Hospital during the period 1963-1982, included 19 patients who survived for 5 years or more after the diagnosis. The clinical data of these patients were retrospectively studied in order to elucidate factors which may have contributed to the more favourable outcome. All of the 5-year survivors were previously untreated, and all had a good performance status at the time of diagnosis. In 95%, the disease was limited to one hemithorax, and 74% had a stage I or II tumour. All treatment modalities, except immunotherapy, were used during the two decades. Surgery alone, or with adjuvant radiotherapy, and/or chemotherapy, was the primary treatment in eight of the long-term survivors (42%). Chemotherapy, either alone or in combination with radiotherapy, was the primary treatment in 10/19 (53%) patients and radiotherapy alone was given to one of the 5-year survivors. The objective response rate to the primary treatment was 100% and complete response was achieved in 95%. There were seven carcinoma related deaths after 5-year disease-free survival. The first site of relapse was the central nervous system in three cases and the liver in three cases. Acute myocardial infarction was the cause of death in five patients. One patient died of the other carcinoma and six are still alive with no evidence of SCCL. In conclusion, a good performance status at diagnosis, no pretreatment weight loss, the extent of disease and good response to the primary treatment appeared to be prognostically important in the present study. Some patients with very limited disease may benefit from primary treatment comprising surgery and adjuvant chemotherapy.