The lack of a widely available diagnostic test for genital infections with Chlamydia trachomatis, coupled with their often nonspecific clinical nature, have been important factors contributing to the increasing incidence of these infections. Recent studies have more clearly defined the clinical manifestations of C. trachomatis infections, especially mucopurulent cervicitis and pelvic inflammatory disease. In addition, methods for the direct detection of chlamydial antigen in genital secretions have been developed. Although less sensitive than traditional cultural methods, these noncultural methods are more widely available than cultures and can facilitate the earlier recognition and more specific diagnosis of chlamydial genital infections. This article reviews these recent developments and outlines specific applications of tests for diagnostic purposes and for screening of high-risk populations.