Five small cell lung cancer (SCLC) cell lines in culture were established and designated as SBC-1, 2, 3, 4 and 5. SBC-1, 2, 4 and 5 were derived from tumors of intermediate cell histology, and SBC-3 was from a tumor of oat cell histology. All the cell lines represented a characteristic cytomorphology of SCLC when examined by papanicolaou staining and by electron microscopy. Their biological characterstics such as doubling time, clonogenic activity, heterotransplantability in nude mice, and capacity of hormone production in culture revealed that each cell line had a distinct biological feature. The SCLC cell lines reported here would be useful as a tool for cellular pharmacology of new drugs and drug resistance.