This contract provides for independent health monitoring of the NIA aged rodent colonies. There are four rodent colonies covered under this independent health monitoring ? aged mouse colony, aged rat colony, aged hybrid rat colony, and caloric restricted colony. The Project Officer periodically directs the colony contractor to send animals to the independent health monitoring contractor for serological, bacteriological and pathological analysis. Those results are reported back to the Project Officer and assist the Project Officer in maintaining the integrity of the rodent colonies.