Two new triterpenoids, named supinenolone D and neospirosupinanetrione, have been isolated from the neutral benzene extract of the whole herb of Euphorbia supina, and their structures determined as fern-8-en-3,7,11-trione and 7(8 --> 9)abeo-9R-D:C-friedo-B':A'-neogammaceran-3,7,8-trione, respectively, on the basis of chemical and spectral evidence.