Recent emphasis on increasing the availability of nuclear emergency diesel generators (EDG's) has motivated the industry to re-evaluate the maintenance philosophies utilized for these units. Improving availability, while maintaining or enhancing the existing levels of reliability, has become the challenge to nuclear utilities. In order to meet quantified reliability and availability objectives, a renewed approach to maintenance is required. The direction taken includes the initiation of a diagnostic data monitoring and trending program to assess those parameters where such methods have proven to be effective. In addition, prescribed inspections based on historical findings are recommended where needed. Periodic reviews are proposed to provide further program improvement.