A serologic survey of a wild cottontail rabbit (Sylvilagus floridanus) population in southern Wisconsin was conducted from November-March, 1971-72 and November-April, 1972-73, to determine prevalence of antibody against Herpesvirus sylvilagus. Flea burdens on each live-trapped cottontail were quantified by species. All but six of the 5029 fleas collected were Cediopsylla simplex. No correlation was found between flea infestation and viral antibody. Of 101 cottontail rabbits trapped, only six had specific antibody as determined by plaque neutralization in rabbit kidney cell culture. Three of the six developed antibody between January and March of the trapping season. Blood samples from 46 captured rabbits were negative for virus.