9The organism is an obligate intracytoplasmic parasite in the family Rickettsiaceae. It causes Q fever in man and occasionally outbreaks of abortions in food animals such as sheep, goats, and dairy cows. The purpose of this report is to describe the pathology and microbiologic findings of a recent outbreak of abortion in sheep from northcentral California. Four aborted near-term lambs and 2 placentas were submitted for diagnostic examination to the Animal Disease Research and Diagnostic Laboratory of South Dakota State University, Brookings, South Dakota, in January 1987. They were submitted from a north-central California flock that had abortions occurring since October of the previous year. The disease appeared to be highly contagious, with the abortion rate varying from 10 to 60% within groups of the flock. Lambs were either aborted near term or born weak. Standard diagnostic procedures for ovine abortions were employed, including gross examination and collection of lung, liver, myocardium, brain, and placenta for histopathology in 10% neutral buffered formalin. For electron microscopy, formalin-fixed tissue was rinsed and postfixed in 2% glutaraldehyde and 1% osmium tetroxide and processed by standard procedures. Lung, placenta, and stomach contents were cultured by standard aerobic and microaerophilic methods. Impression smears were prepared from placental cotyledons and stained with Gimenez stain. Fluorescent antibody tests were done on frozen placental sections using Chlamydia groupspecific conjugate” and conjugate specific for C. burnetii.