The occurrence of helminth parasites of barbel in the Doganci Dam Lake was investigated monthly from December 1998 to November 1999. During this study, a total of 47 barbell were caught and examined for helminth parasites. A total of 5 species of helminth parasites was found as follows. Dactylogyrus carpathicus (Monogenea) was observed on gills of the fish and Bothriocephalus acheilognathi, Caryophyllaeus laticeps (Cestoda), Allocreadium isoporum (Digenea) and Contracaecum sp (Nematoda) were present in the intestines and the abdominal cavity of fishes. D. carpathicus was the dominant parasite species found in barbel. A total of 117 parasites were recorded on 27 of the 47 fish examined. The overall prevalence of D. carpathicus was 57%. A. isoporum was the second most dominant parasite in this study. A total of 35 parasites were found in 9 of 47 fish examined and the total prevalence of A. isoporum was 19.1%. However B. acheliognathi were present only in very small numbers. Only seven B. acheliognathi were found in 4 of the 47 fish examined. Four fish were infected by C. laticeps and a total of 13 parasites was found. A single species of Nematoda, Contracaecum sp was observed in 5 of the 47 fish examined. A total of 25 parasites was recorded. The overall prevalence of Contracaecum, sp was 27.2%. D. carpathicus and A. isoporum were new records for the helminth fauna of Turkey.