Semi-quantitative RT-PCR was applied to investigate the developmental patterns of GH-R, IGF-1 and IGF-IR mRNA expression in skin of two sheep breeds. One breed was the first filial generation (F1) of Romilly Hillys x Merino of China (Xinjiang Agricultural Reclamation line) wool sheep, and the other was Kazak hair sheep. 18S rRNA was used as the internal standard. Sheep were weighed and wool and skin samples were collected at different times. Results showed that body weight increased rapidly during 30-135 days but slowed during 135-255 days. Wool growth increased gradually during 30-135 days, degreased till 180 days of age, but rebounded thereafter. Overall, body weight and developmental patterns of wool growth was not significant different between hair and wool sheep. GH-R mRNA expression in the skin of hair sheep increased significantly during 30-90 days, peaked at 90 days of age (P<0.05), then declined signifi cantly (P<0.05). GH-R mRNA expression in the skin of wool sheep increased significantly until 135 days of age (P<0.01) and then decreased significantly (P<0.01). The peak level was higher in the wool sheep than the hair sheep. The expression of cantly IGF-1 mRNA and IGF-IR mRNA in the skin of hair sheep increased during 30-90 days, then declined significantly (P<0.01). The expression of IGF-1 mRNA and IGF-IR mRNA in the skin of wool sheep were high at birth and then reduced gradually. The IGF-1 mRNA expression in the skin of hair sheep reached its peak at 90 days of age, and was significant higher than that of wool sheep. The expression of GH-R, IGF-1 and IGF-IR mRNA in skin of hair sheep was higher than that of wool sheep before 90 days of age, but was lower after that. The results suggest that GH-R, IGF-1 and IGF-IR mRNA expression in the skin of sheep follows specific developmental patterns, and different patterns exist between the two breeds.