The Awassi population (22,000 ewes) of the Ceylanpinar State Farm, situated in south-east Anatolia, is used to produce both meat and milk under a semi-intensive system of management. Rams of the intensively managed Israeli Improved Awassi type were introduced to the Ceylanpinar flock and both growth and milk production were monitored between 1993 and 1999. Individual performance of lambs and yearling ewes were recorded and analysed by genotype (Ceylanpinar (C), Israeli Improved Awassi (I)xCeylanpinar (F1), CxF1 (B1C), IxF1 (B1I), B1CxC (132C.C). Using least-squares analysis to account for the effect of flock, year, sex, birth type and weaning age, the least-squares mean weaning weights for male lambs of the different genotypes were 18.3 (C), 19.3 (F1), 19.7 (B1I), 18.3 (B1C) and 18.2 (132C.C) kg. Similar trends were found for other growth traits. Least squares analysis of milk production between days 90 and 150 of lactation and the 120 days post weaning also demonstrated a superiority of F1 and B1I over C ewes. The offspring of the highly selected Israeli Improved Awassi genotypes, from an intensive production system, were found to give higher performance than local sheep, in a semi-intensive system. Increases of between 5 (growth) and 20% (milk) were found when comparing the F1 to the Ceylanpinar sheep. (C) 2001 Elsevier Science B.V. All rights reserved.