A fluorescent antibody staining method was developed to detect Chlamydia trachomatis elementary bodies in Papanicolaou-stained cervical smears. Twenty-five known chlamydia-positive and 12 chlamydia-negative smears were correctly identified using this method. Smears from individuals with culture-positive chlamydia infections showed a high density of elementary bodies. Among 64 routine cervical smears, 27% (6/22) of smears that showed inflammatory changes were positive by fluorescent antibody staining for chlamydia, compared to 2.4% (1/42) of smears that were negative for inflammatory changes. This method should facilitate detection of chlamydia infections in populations undergoing cytological screening.