A mycoplasma survey of goats with a history of mastitis, polyarthritis, and pneumonia revealed a high incidence of Mycoplasma mycoides subsp mycoides (large-colony type). During the early winter kidding season of 1979-1980, kid morbidity in a large commercial dairy herd, evidenced by hyperthermia, polyarthritis, and pneumonia, exceeded 90%. In excess of 200 kids died. Colostral cultures of the parent does yielded 157 isolations from 605 goats (26%). Additional isolations were made from goats with polyarthritis, peritonitis, CNS disorders, and pneumonia; these animals represented 6 California counties and the states of Arizona and Idaho. Identification was accomplished by growth inhibition and immunofluorescent studies. Titers in the colostrum, although variable, were as high as 1 x 10(10) viable organisms/ml and remained virtually undiminished after storage at 5 C for periods of greater than or equal to 4 weeks. The experimental inoculation of the organism into normal goats 1 week to 2 years of age resulted in the death of most animals between the 4th and 14th day after inoculation, whether the organism was administered intraperitoneally, IM, into the teat canal, or orally to young animals. The primary lesions were a fibrinopurulent polyarthritis, fibrinous pleuritis, and pneumonia. It appears that goats can acquire the infection through ingestion, and the organism seems to be widespread in the United States.