The predominantly myeloid cell–expressed C-type lectin-like receptor dectin-1 is a pattern-recognition receptor that recognizes ß1,3-linked glucans found in fungi, plants and some bacteria, as well as an unidentified ligand on Mycobacteria sp. There is a further uncharacterized endogenous ligand on T lymphocytes and apoptotic cells. Dectin-1 is a type II transmembrane-spanning molecule with a cytoplasmic tail, containing a nonclassical immunoreceptor tyrosine activation-like (ITAM-like) motif, and a single extracellular carbohydrate recognition domain. Two major isoforms exist—dectin-1A and dectin-1B—the difference being the presence or absence, respectively, of a stalk region that separates the carbohydrate recognition domain from the transmembrane domain. The mouse dectin-1 expression profile is restricted to myeloid cells and subsets of T lymphocytes, whereas the human homolog is also expressed on B lymphocytes and eosinophils. Expression levels are modulated by a variety of cytokines and other immune response modifiers, and isoform expression profiles differ according to cell type and mouse genetic background. Interaction of dectin-1 with its exogenous ligand results in the triggering, through its cytoplasmic ITAM-like motif, of respiratory burst, phagocytosis, production of various cytokines and chemokines, arachidonate metabolism, and dendritic cell maturation. Dectin-1 is able to function independently, as well as collaboratively with the Toll-like receptors, to modulate immune responses. Dectin-1 mediates signaling through spleen tyrosine kinase, Raf-1 kinase and other undefined pathways. The generation of a dectin-1 knockout mouse has indicated a role for this receptor in the recognition and control of fungal pathogens, although the full extent of its importance in antifungal immunity is unclear. Triggering of dectin-1 on dendritic cells can induce strong CD4+ and CD8+ T-cell responses and skew the adaptive response toward T-helper type 1 and type 17 profiles. Dectin-1 therefore functions as a classical pattern-recognition receptor and is able to link the innate and adaptive immune responses.