A total of 116 women were referred for hysterosalpingography because of primary or secondary infertility. Chlamydia trachomatis was isolated from the cervix of four (3.4%) of the patients whereas Mycoplasma hominis was isolated from 39 (33.6%) of them. Four patients developed acute pelvic inflammatory disease after hysterosalpingography; two of them were chlamydia culture-positive and developed a significant chlamydial antibody response during the course of the disease. One of the other two patients, who developed upper genital-tract infection, was culture positive for M. hominis and developed a significant antibody response to this micro-organism. The results indicate that C. trachomatis should be sought in patients before hysterosalpingography and, if detected, appropriate antibiotic cover should be instituted before the procedure.