Abstract The solid state forms of troglitazone drug substance and diastereomers were characterized using solid state nuclear magnetic resonance (SSNMR) spectroscopic method. The SSNMR spectroscopy could distinguish the hydrated and the non-hydrated RR/SS forms more clearly than powder X-ray diffractometry (PXRD). The SSNMR result supported that troglitazone drug substance consists of diastereomers as a simple physical mixture. SSNMR spectroscopy was also able to characterize the solid state forms of troglitazone in tablets while PXRD was unable to because of interference from the pharmaceutical additives. Troglitazone was proved to exist in amorphous form in tablets, and keep its solid state form amorphous against heat and humidity. SSNMR spectroscopy thus provides very important information for the development of the pharmaceutical formulation of troglitazone.