We investigated olfactory function and its relation with cardiac 123I-metaiodobenzylguanidine (MIBG) uptake in 15 patients with drug-induced parkinsonism (DIP). The mean Cross-Cultural Smell Identification (CCSI) score was significantly greater in patients with DIP than in those with Parkinson¡¯s disease (PD; 6.9 ¡¾ 1.6 vs 4.4 ¡¾ 2.2, p<0.001); however, the mean CCSI score in patients with DIP was not statistically different from control. One patient with DIP, whose CCSI score was significantly reduced, also exhibited decreased cardiac MIBG uptake. The DIP patients with CCSI scores within the normal range had normal cardiac MIBG uptake. Our study suggests that an olfactory function test may be a useful tool for detecting DIP unrelated to PD and for identifying patients with DIP who have subclinical PD.