The effect of BCNU, Cyclophosphamide (CY) and surgery treatment was studied in mice inoculated s.c. with LL cells. With BCNU given in a single 40 mg/kg dose 24V h after s.c. implantation of 2 X 10(6) tumor cells only increase in life span (ILS) was observed while with CY given in a dose 300 mg/kg at the same time it was possible to cure the tumor-bearing mice. However, if the drugs were administered on day 8 when the average tumor mass was about 548 mg and the micrometastases in the lung were detectable, only an increase in life span could be achieved. The combination of surgery and CY in advanced tumor bearing mice resulted again in the high percentage of cures.