Diosgenin in 18 samples belonging to 3 species of Costus L. was determined by colorimetric and GC analyses. The results indicated that the content of diosgenin in Costus lacerus rhizome is the highest (0.530%) and the content in C. speciosus C. lacerus . It also showed that C. tonkinensis contains no diosgenin. The samples from different parts, ploid races, locations, collection periods and storage conditions contain various amounts of diosgenin.