Inoculation of the mouse pneumonitis biovar of Chlamydia trachomatis into the ovarian bursa of mice resulted in salpingitis. An acute inflammatory response in the bursa and contiguous oviduct peaked at six to nine days postinoculation. At day 14, most animals showed an acute and chronic infiltrate that occluded the oviductal lumen in some sections. Inflammatory exudate and debris accumulated in the periovarial space near the ostium of the oviduct. Inclusions were demonstrated in the lumenal epithelial cells of the oviduct and uterus. The mouse pneumonitis agent could be recovered from genital tissues for up to 21 days postinoculation but not from other organs. IgG antibodies to the mouse pneumonitis agent were detected at seven days postinoculation and reached peak titers by 21-30 days. By 25-30 days postinoculation, the inflammatory reaction declined and hydrosalpinx was observed. This model for salpingitis may be useful in understanding some aspects of the pathogenesis of C trachomatis genital infections.