WGA-receptors on the surface of resident guinea pig peritoneal macrophages were investigated. Macrophages were characterized by the endogenous peroxidase pattern. Two different immunogold techniques, the indirect WGA-anti WGA-protein A-gold technique and the direct WGA/BSA-gold technique were compared to evaluate their suitability for quantification of WGA binding sites on the cell surface. Because of the higher binding specificity the direct technique should be preferred for quantitative studies.