The 1-monostearate and the distearate of pro-pylene glycol were prepared with racemic propylene glycol and L ( + ) propylene glycol, and their crystal properties were compared. Racemic propylene glycol-l-monostearate shows four dif-ferent polymorphic modifications whereas opti-cally active propylene glycol-1-monostearate is monomorphic, with a melting point of 54.0C and a long spacing of 50.6A. Racemic propylene glycol distearate has an unstable Form II, which transforms irreversibly to Form I near 44C. Form I melts at 58.8C. The two forms have long spacings of 53.4A (Form II) and 43.4A (Form I). Optically active propylene glycol distearate exhibits three crystalline modifications: an un-stable Form II which transforms irreversibly to Form I near 37C, with Form I melting at 53.9C, and a third, stable form, termed Form III, melt-ing at 58.80. The long spacings of the three forms are 51.9A, 43.6A, and 46.9A respectively. Heats of transition for the various phase changes are given.