Chlamydia trachomatis serovar was determined by analysis of restriction fragment length polymorphism in the gene encoding the major outer membrane protein (MOMP) from 435 urogenital specimens. Of the specimens, 254 grew <25 inclusions and 14 were negative in culture. Although previous studies defined serovar by epitopes or sequences representing only the four variable domains in MOMP, restriction endonuclease sites characteristic for each serovar not only within but also outside these variable domains were cataloged in this study. Novel serovars that grew poorly or not at all in vitro were not observed, and all samples proved similar or identical to one of the 15 known serovars. There was no significant difference in proportions of serovars between men and women. In women, F serovars were more frequently observed in infections with few inclusions in culture, whereas B group serovars predominated when many inclusions were observed.