Araujo. F. P. (School of Veterinary Medicine, Univ. of California. Davis, CA 95616), C. W. Schwabe, J. C. Sawyer and W. G. Davis. Hydatid disease transmission in California: a study of the Basque connection. Am J Epidemiol102:291–302, 1975. A descriptive epidemiologic and anthropologic study was designed to determine by field observation and interview the extent of Basque involvement in the sheep industry of California, the nature of the sheep and dog husbandry practices of California Basques as theymight influence Echinococcus granulosus transmission, and the “folk knowledge” of hydatid disease possessed by California Basques, particularly as it might indicate the early presence of this infection in California and provide evidencefor or against possible intensification or spread of transmission in the recent past. Basques were found to dominate the sheep industry of California's Central Valley from Sacramento south, but to be virtually absent from other sheep-raising areas of the state. In contrast to most other California sheep ranchers, Basques practice a transhumant form of husbandry in which bands of sheep are moved from location to location under the control of contract Basque shepherds from Spain and France and a number of sheep dogs. These dogs feed mostly on dead sheep and deposit their feces over large areas of crop and recreationallands. Some of them come into frequent contact with persons outside the sheep industry. Few California Basques recognize hydatid disease in their sheep and they possess no knowledge of its presence prior to the initiation of our studies in 1967. These findings tend to confirm earlier evidence that the distribution of echinococcal infection in California now is widespread but highly focal.