The Texas Department of Health Laboratory cultured arthropods from November 1988 through December 1989 in an attempt to isolate Borrelia burgdorferi, the etiologic agent of Lyme disease. Spirochetes were isolated from eight of 1,093 pools of arthropods cultured. The spirochetal isolates were from several tick and one flea species, including Amblyomma americanum, A. maculatum, Ixodes scapularis, and Ctenocephalides felis. These 8 isolates reacted specifically when treated with monoclonal antibodies to B. burgdorferi. Polyacrylamide gel electrophoresis of six lysates showed them to be virtually identical with strain B31 of B. burgdorferi.