Abstract: Following an initial report of Mycoplasma mastitis in Ardabil state dairies, a survey of milk samples from a random group of dairy farms was conducted in Moghan area in ardabil state,Iran. Cows (n = 80) from four farms (4 cooperative farms consisting of 10550 cows/herd) with clinical mastitis and bulk milk tanks(n = 48) were monitored and sampled for clinical mastitis. A total of 80 aseptic milk samples were collected when an clinical mastitis was occurred (based on any observable signs in the udder and/or milk) and delivered to the national mastitis laboratory. Untreated samples obtained by haulers were cultured for enrichment of mycoplasmas on selective media. Samples from 4 farms obtained between February and April 2005 were examined and the incidence of positive samples was 48.75%.(39 positive sample of 80 milk samples) M.bovis presence was detected by immunoproxidase test in all of the positive sample.Detection of infection in bulk tank samples and cow milk samples was done at the high sensitivity for the techniques used, indicating that high concentrations of the mycoplasmas were to be found in such samples. Development of routine diagnostic capabilities for the diagnosis of mycoplasmal mastitis should be considered in Moghan to minimize the impact of this disease in dairy herds.