In Hann:Wistar rats, 25 weekly subcutaneous injections of dipentylnitrosamine (DPNA) at doses of 0, 62.5, 125 and 250 mg/kg body weight induced lung carcinomas which metastasized partly. The incidence of the primaries was 2.5, 20.0, 77.5 and 100% in the males and 0, 0, 12.5 and 57.5% in the females, respectively. The frequency of metastases was 0, 12.5, 38.7 and 72.5% in the males and 0, 0, 40.0 and 52.2% in the females, respectively. The most common metastatic sites in males and females together were: lung-associated lymph nodes (82.1%), adrenal gland (53.6%), kidney (39.3%), pancreas (32.1%), bones (16.1%), heart (12.5%), mesentery (12.5%) and CNS (8.9%). In the females, metastases were also detected in the uterus (21.4%) and ovary (42.9%). The results indicate that: (1) through subcutaneous injections of DPNA metastasizing lung carcinomas can be induced with high incidence, and (2) the metastatic pattern is very similar to human cases. Thus, this model could be useful for the study of metastasizing lung carcinomas in experimental animals.