Serotyping of strains of Mycoplasma hominis, freshly isolated from various sources, was conducted using the complement-independent growth agglutination (GA) test, using the 7 reference antisera prepared in our laboratory. Multiple isolates from a common source indicated that only a single serotype tends to be found, making it possible to serotype clinical isolates without further cloning. However, cultures collected at different times from the same individual may contain different serotypes. A total of 213 recent cultures were serotyping and a majority of these were assigned to the closely related serogroups 1, 2, and 3. Strains isolated during pregnancy, that were associated with various disorders of pregnancy, were serotypically diverse and no one strain seemed to be particularly likely to be associated with disorders of pregnancy.