Web proxy caches are used to improve performance of the WWW. Since the majority of Web documents are static documents, caching them at WWW proxies reduces both network traffic and request response time. One of the keys to better proxy cache performance is an efficient caching policy which keeps in the cache popular documents and replace rarely used ones. This paper introduces the Greedy-Dual-Size-Frequency caching policy to maximize hit and byte hit rates for WWW proxies. Proposed caching strategy incorporates in a simple way the most important characterizations of the file and its accesses such as file size, file access frequency and recentness of the last access. Greedy-Dual-Size-Frequency is an improvement of Greedy-Dual-Size algorithm - current champion among the replacement strategies proposed for Web proxy caches. 14 Pages