In present study, the developmental patterns of myoglobin (MB) mRNA expression were compared between Erhualian and Large White boars, Gender difference was also examined in Erhualian pigs. Semi-quantitative RT-PCR was applied to determine the level of MB mRNA. Different developmental patterns were observed in two breeds of pigs. MB mRNA expression was low in both breeds at D3, while divergent trends were followed by different breed of pigs thereafter. No significant changes in MB mRNA expression were observed in Large White boars over the period of investigation, although a higher level was seen at D120. In Erhualian boars, however, the level of MB mRNA increased significantly (P<0.01) from D3 to D20 and stayed high consistently afterwards. As a result, Erhualian boars expressed higher level of MB mRNA in Longissimus Dorsi muscle compared with Large White boars on 20, 90, 120 and 180 days of age. Similar patterns of MB mRNA expression were found in both sexes of Erhualian pigs, except at D180, a remarkable decrease occurred to females (P<0.01), resulting in a significant (P<0.01) gender difference at D180 with higher level of MB mRNA expressed in Erhualian boars.