Pedigrees of ewes with Ringwomb were studied to determine the etiology, incidence and treatment of Ringwomb. Purebred Suffolk and crossbred Hampshire and Shropshire ewes aged from one to seven years were observed over a period of five lambing seasons. The study was conducted on 24 clinical cases of ringwomb occurring in one flock. Ringwomb or incomplete cervical dilation accounted for an incidence of 20.5% (24/117) of all ewes lambing. The ewes affected were all daughters, granddaughters, or great-granddaughters of one particular sire used on the farm as a service sire. Because ringwomb does not typically affect ewes in two consecutive seasons, it is concluded that the occurrence of ringwomb is dependent upon the genotype of the fetus. The author concludes that the service sire introduced an autosomal recessive gene into the ewe flock and that the phenotype was not displayed until the carrier daughters were serviced by another carrier