BACKGROUND: Group A bovine rotavirus (BRV-A) is one of the most important causes of gastroenteritis and diarrhea in newborn calves. OBJECTIVES: Major types of BRV-A in Tehran, Alborz and Qazvin were detected in this study. METHODS: A total 125 fecal samples of calves showing clinical signs of diarrhea were collected from 26 industrial dairy farms located in the provinces of Tehran, Alborz and Qazvin, during two years. RESULTS: BRV-A was detected in 39.2 % (49/125) of total samples using a commercial ELISA kit. Thirty five positive samples were analyzed by seminested multiplex RT-PCR for P and G genotyping. G10 was the most prevalent genotype, accounting for 57.1% of samples, G6 accounted for 22.9% of samples and in 5.7% of samples (2/35), mixed infection of both genotypes G6 and G10 were detected. Also, the detected P types were P[11] and P[5], accounting for 71.4% and 14.2%, respectively. In our study, none of the genotypes G8 and P[1] were detected. The incidence of genotype combinations cor-responded to the B223-like strains (G10P[11]), UK-like strains (G6P[5]) and KN4-like strains (G6P[11]) were 51.4%,14.3% and 8.6%, respectively. Mixed infections G6/G10P[11] were detected in 2.85% of all samples analyzed with RT-PCR. CONCLUSIONS: To the best of our knowledge, this is the first report about the determination of P genotypes of BRV-A and distribution of the most common BRV-A strains circulating in Iran. Our study also indicated that the incidence of the G genotypes of BRV-A in the provinces of Tehran, Alborz and Qazvin, which is one of the greatest husbandry centers in Iran, has changed in the past years. Furthermore, this finding could be valuable in rotavirus vaccine design.