Dectin-1 is a pathogen-recognition receptor on macrophages (MΦs), neutrophils, and dendritic cells (DCs). On MΦs and bone marrow-derived DCs, it has been shown to mediate the nonopsonic recognition of and response to soluble and particulate yeast β-glucans. We have optimized the immunohistochemical detection of Dectin-1 and demonstrated its expression on neutrophils, subpopulations of MΦs in splenic red and white pulp, alveolar MΦs, Kupffer cells, and MΦs and DCs in the lamina propria of gut villi. This is consistent with its role in pathogen surveillance. A significant proportion of CD11c⁺ splenic DCs expressed Dectin-1, but expression was not restricted to any one subset. Dectin-1 expression was low on resident MΦs and DCs of skin and was not detected on resident MΦs or DCs in kidney, heart, brain, or eye. The proposed, additional role of Dectin-1 as a coreceptor for T cell activation is supported by its expression on DCs in the T cell areas of the spleen and lymph nodes. Strong expression of Dectin-1 on subpopulations of MΦs and DCs in the medullary and corticomedullary regions of the thymus suggests a role distinct from pathogen recognition. Tissue localization thus revealed potential roles of Dectin-1 in leukocyte interactions during innate immune responses and T cell development.