OBJECTIVE To determine the effectiveness of postexposure rabies prophylaxis (PEX) recommendations, as mandated by the state of Texas, and to investigate PEX and preexposure rabies vaccination failures. METHODS Retrospective study. METHODS 1,345 unvaccinated domestic animals that had received PEX and 6 animals that had preexposure rabies vaccination failure. METHODS Zoonotic incident case report forms from 1979 through 1994 were reviewed for information about unvaccinated domestic animals that received PEX after exposure to a rabid animal, according to state protocol; the reports were also reviewed for information about preexposure rabies vaccination failures. From 1979 through 1987, the PEX protocol was to immediately vaccinate the animal against rabies, isolate it for 6 months, and administer a booster vaccination 1 month prior to release from isolation. From 1988 through 1994, the protocol was to immediately vaccinate the animal against rabies, isolate it for 90 days, and give booster vaccinations during the third and eighth weeks of the isolation period. RESULTS From 1979 through 1987, 713 animals received PEX; 2 failures were recorded. From 1988 through 1994, 632 animals received PEX; 3 failures were recorded. From 1991 through 1994, 6 preexposure rabies vaccination failures were recorded. CONCLUSIONS An effective PEX schedule for domestic animals includes immediate rabies vaccination, with a minimum of 1 booster vaccination, and 90 days' strict isolation.