AbstractThe structure of the hypoglycemic agent Gliclazide has been studied by 1H, 13C, and 15N NMR in solution (CDCl3 and DMSO‐d6) and in the solid state. In the solid state, the compound crystallizes as an EZ isomer without dynamic properties. In CDCl3 solution, the structure is still EZ but with a slow nitrogen inversion about the pyrrolidine nitrogen: two invertomers have been observed and characterized. In DMSO‐d6, the rate is faster and only averaged signals were observed. GIAO calculated absolute shieldings were used to confirm the nature of the observed species. In the solid state, Gliclazide presents the phenomenon of solid‐solution with two disordered conformations present in the crystal at a 90:10 ratio. Copyright © 2009 John Wiley & Sons, Ltd.