The recovery of viruses and Chlamydia trachomatis from cell cultures and the detection of their antigens in impression smears prepared from open-lung biopsy (OLB) specimens from immunocompromised adults were compared. Touch impression smears were prepared on three slides, each containing eight wells. OLB tissue was homogenized (Stomacher) and inoculated into MRC-5, primary monkey kidney, and McCoy cell cultures. The direct and indirect immunofluorescence (IF) tests were used to detect antigens to the following organisms: herpes simplex virus, adenovirus, parainfluenza types 1 and 3, respiratory syncytial virus, cytomegalovirus (CMV), Chlamydia trachomatis, influenza types A and B, and varicella-zoster virus. Of 105 OLB specimens, 21 viral isolates (20%) were recovered in cell culture; 20 were CMV and one was an influenza virus type A (H3N2). Both culture and IF results were positive with 12 specimens, but in nine instances a virus was isolated and IF was negative or eight times culture results did not yield the organism but IF test results were positive. Chlamydia trachomatis was never isolated or detected by IF. The authors recommend that for optimal detection of CMV from OLB specimens a new rapid centrifugation-enhanced cell culture system be used in preference, or in conjunction with a preliminary IF screen of impression smears for CMV detection.