To evaluate the sensitivity of Monilinia fructicola to dicarboximides used in controlling brown rot of peach, the fungus was isolated from commercial peach orchards in Chochiwon (CH), Chongdo (CD), Gyeongsan (GY), and Youngduk (YO) in Korea. The population shift of dicarboximide-resistant isolates of M. fructicola was investigated for 3 years starting 1998. The frequency of procymidone-resistant isolates (PRI) was higher in CD and GY than in CH and YO. The frequency of PRI was higher in the mid season (July-August) than in the rest of the year. Cross-resistance rate of PRI to iprodione was over 87.8% during the investigation, and doubleresistance to both procymidone and carbendazim was less than 10%. However, the rate of cross-resistant isolates to vinclozolin was low. In the orchards in GY and CH without any fungicide spray, the PRI population was persistent and did not vary for 3 years. The results suggest that dicarboximide resistance of M. fructicola could be a problem in controlling brown rot and blossom blight on peach trees because it may take a long time to recover the population with sensitive isolates even in the absence of these fungicides.