The 24 vests in the test came from the same production lot. They were made of Kevlar fabric and included eight that were unused, four that showed light wear, four that showed moderate wear, and eight that showed heavy wear. The results of the ballistic tests were not significantly affected by whether the vests were wet or dry when tested. The body armor also retained full ballistic efficiency when stored under typical warehouse conditions for periods of more than 10 years. Ballistic efficiency tended to increase as a consequence of light to moderate wear. A slight decrease in efficiency occurred with heavy wear, but it was not clear whether the change related to the wear or to differences between individual samples. The possible trend of decreased efficiency following heavy use, coupled with the identification of at least two armor panels lacking waterproofing, suggested the need to inspect vests in use annually. Samples of vests showing extremely heavy wear should be tested for ballistic performance when they are wet. Photographs, data tables, appended tables, 5 references, recommended test conditions.