A human embryonal carcinoma (EC) cell line, NEC14, was pluripotent and the tumors formed in nude mice contained differentiated somatic and extra-embryonic elements in addition to EC. The NEC14 cells could be induced to differentiate with 5 differentiation inducers in vitro, and N,N'-hexamethylene bisacetamide (HMBA) showed the most potent differentiator induction among them. All of the NEC14 cells were morphologically differentiated when exposed to 10(-2) M HMBA for 3 days. The differentiated derivatives ceased to proliferate in vitro and became non-tumorigenic in nude mouse. Several differentiation markers appeared in the differentiated derivatives. When the tumor-bearing nude mice were injected intraperitoneally with HMBA (10mg, twice a week), the tumor growth was inhibited. These results show that human EC is a useful model of differentiation-induction in cancer therapy.