Bacterial isolations were attempted from milk samples taken from 242 range ewes in a southwestern Idaho shed lambing enterprise. Eighty-five percent of the ewe milk samples had no pathogenic bacterial growth at lambing and 3 weeks later. The few organisms that were isolated did not appear to affect udder condition of the ewe or contribute to lamb mortality. Shed conditions did not affect the frequency of isolation of potentially pathogenic bacteria. The prevalence of udder abnormalities, however, did appear to have a positive association with ewes that lost theim lambs. The most frequent abnormality was a diffuse homogeneous induration of the udder. This hardening was apparently unrelated to bacterial isolation or the age of the ewes. Mastitis, either subclinical or clinical, did not appear to be a serious problem in this particular flock. Mastitis was not related to lamb mortality.