Abstract. The goals of this study were to compare the mRNA expression profiles of growth hormone recep tor (GHR) and insulin-like growth factor I (IGF-I) in various tissues of cattle and the semi-wild yak (Datong yak) and to find out whether the mRNA levels of the two genes are correlated. The mRNA levels of GHR and IGF-I in heart, lung, liver, spleen, pancreas, kidney, muscle, mammary gland and ovary of cattle and yak were investigated by using quantitative real-time po ly mer ase chain reaction (PCR). The experiments showed that the transcript levels of the two genes were signif icantly higher in liver (P<0.05) than in the other tissues for both species and that IGF-I levels varied more among tissues (P<0.01) than did GHR levels. The GHR tran script level in pancreas was higher in yak (P<0.05) than in cattle. There was no statistically sig nif i cant difference in IGF-I tran script levels among all the tissues of both bovine groups. Growth hormone receptor and IGF-I transcript levels were positively correlated in mammary gland (P<0.01), lung (P<0.05) and muscle (P<0.05) in yak, negatively correlated in cattle heart (P<0.05) and not correlated in the other tissues. The results indicate that the two genes are reg u lated differently in various tissues under normal physiological conditions in these two bovine species.