The results of planned population surveys for opisthorchiasis performed by teams of epidemiologists in 11 districts of Chernigov Province have been reviewed. 130,067 individuals in 156 communities have been examined. All the communities were situated not more than 5 km from the main water artery of the area--the Desna River and its main tributaries--the Seim, the Ubed', the Doch', the Borzna. 713 cases of opisthorchiasis have been identified in 96 villages. 1.0 +/- 0.2% (out of 3,180) of mollusks C. inflata and 0.9 +/- 0.4% of carps from the river basins in 8 districts of the region proved to be invaded with Opisthorchis larvae.