An indirect fluorescent antibody technique has been developed for the serological diagnosis of gonorrhea. The selected strain(s) of Neisseria gonorrhoeae possesses a heat-labile surface antigen (L-antigen). Sera are diluted 1:10, and an aliquot is hear inactivated at 59 C for 30 min. The treated and untreated aliquots are then examined for human immunoglobulin G anti-L-antigen. In a prelimiary study of 495 sera, 95% of those from women with a bacteriologically confirmed diagnosis of gorrhea and 87% of those from male patients were reactive in this test, whereas only 1.4% fo the sera from presumably normal individuals were reactive.