Hybridization between Leuciscus cephalus and Cholcalburnus chalcoides was identified from biometrical features in 55 fish caught from Lake Todurge, Sivas, Turkey, between April 1994 and November 1997. The hybrid index V-h for metric and meristic characters was intermediate (V-h = 45.6) compared with their parents (L. cephalus VI, 0 or negative and C. chalcoides V-h >= 100). Morphological, metric and meristic features of L. cephallis x C. chalcoides also resembled those of the parents. The majority presented an intermediate position which was best shown by the shape of mouth, caudal fin, gill rakers and pharyngeal teeth, and also by the caudal peduncle depth, head and interorbital width, predorsal and preanal distance, height of anal fin, length of anal base and other characters. (c) 2005 The Fisheries Society of the British Isles.