<p>Disclosed are an optically active thiazolidinedione derivative, a pharmacologically acceptable salt thereof, and a pharmaceutical product containing any of them. The optically active thiazolidinedione derivative can be obtained by optical resolution of (RS)-5-{4-[(6-methoxy- 1-methyl-1H-benzoimidazol-2-yl)methoxy]benzyl}-1,3- thiazolidine-2,4-dione.</p>
