Concentrated Liu-wei-di-huang decoc-tion[An ancient Chinese prescription consistsof Rehmannia glutinosa Libosch.

Cornusofficinalis Sieb.et Zucc.

Dioscorea oppositaThunb.

Poria cocos（Schw.）Wolf.

Paeo（?）iasuffruticosa Andr.

Alisma orientalis（Sam.）Juzep.]administered at a dosage analogous to20g.crude drug/kg./day for 17 weeks sup-pressed the development of urethan（1.0mg/gr.）-induced lung tumor in male mice.Inour laboratory

the incidence of spontaneouspulmonary adenomas in normal male micewas 0.05±0.05/mouse（Mean±S.E.）.Thenumber of pulmonary adenomas in urethan-induced mice was 6.61±1.12

while that ofthose treated with Liu-wei-di-huang decoc-tion was 2.89±0.47（P<0.01）.The me-chanism of the prescription is briefly discus-sed.