The decomposition of 25α-Δ 5 -spirosten-3β-ol (diosgenin) has been studied by various physical techniques in the solid state, in contact with both 2 N hydrochloric acid and 2 N sodium carbonate solution, and in solution in both chloroform and benzene. In contact with 2 N hydrochloric acid, about 40 percent of the diosgenin was found to decompose within 4 months, whereas in the other conditions, the amount of decomposition was found to be negligible, although decomposition products were detected on thin-layer chromatograms and by ultraviolet spectroscopy.