A study was made on the Monogenea of 417 Cyprinus carpio. Carp were captured monthly between May 1990 and September 1991 in the central basin of the Llobregat river in the NE of Spain. Gyrodactylus cyprini, G. katharineri, Dactylogyrus anchoratus, D. extensus and Dactylogyrus minutus were identified on these fish. Gyrodactylus cyprini, G. katharineri and D. minutus are recorded in Spain for the first time. Gyrodactylus spp. have always been found on the fins and skin and Dactylogyrus spp. were found on the gills. Gyrodactylus spp. infected 19.42% of the hosts and Dactylogyrus spp. infected 72.42% of the fish. All the parasites had a clear seasonal occurrence.