Using standardized laparoscopy technique, fluid was aspirated from the pouch of Douglas, from the Fallopian tubes and from ovarian cysts in 85 cases with clinical diagnosis of pelvic inflammatory disease (PID). The concentration of doxycycline in the aspirates was measured after oral ingestion of 200 mg of doxycycline (Vibramycin). A therapeutic level was achieved in the tubes and in ovarian cysts within a few hours, and on continuation of the treatment these values followed the plasma concentration closely, still being within the therapeutic range 24 hours after the final dose. The clinical effect was excellent, 94% (60/64) of the cases with verified PID being cured by doxycycline.