Previous studies have indirectly shown that type 1 gonococci are more resistant to phagocytosis by human neutrophils (PMN) than type 3 gonococci. Using phase contrast, fluorescent, and light microscopy, we directly quantitated PMN-gonococcal interaction, with emphasis on separating ingestion from attachment. PMN monolayers were incubated on slides with type 1 or type 3 gonococci. The slides were iced to stop phagocytosis and stained with antigonococcal fluorescent antibody (FA). After methanol fixation, the FA-stained gonococci associated with PMN were counted. Since the live PMN excludes FA, the FA-stained gonococci represent only extracellular gonococci. Methylene blue was then added to the same slide to stain both ingested and surface attached gonococci. Using these methods, intracellular and extracellular cell-associated gonococci were quantitated under varying conditions. The numbers of methylene blue-stained cell-associated gonococci were similar for types 1 and 3. The proportions of cell-associated gonococci that were ingested were: with normal serum, 3.7 4.1% for type 1 and 56.2 i 3.5% for type 3 (P < 0.001); with heat-inactivated serum, 1.0 + 3.0% for type 1 and 52.6 3.7% for type 3 (P < 0.001); with high-titer anti-gonococcal antibody serum, 4.8 + 4.3% for type 1 and 64.0 1.6% for type 3 (P < 0.001). Thus, most type 3 organisms were ingested, but most type 1 gonococci were bound on the PMN surface.