Zymosan particles have served as a model for recognition of microbes by the innate immune system for over 50 years. Zymosan induces inflammatory signals in macrophages through Toll-like receptors TLR2 and TLR6. In addition, phagocytic receptors on macrophages bind zymosan and stimulate particle engulfment. We have further examined the requirements for induction of inflammatory responses such as TNF-alpha production and NF-kappaB activation by zymosan in mouse macrophages. We have observed that direct particle contact is required (excluding a role for soluble components of zymosan preparations) and that contact with a single particle is sufficient to trigger cytokine production. Further, ablation of the Toll-like receptor-stimulating activity of zymosan does not affect the ability of phagocytic receptors to internalise the particle.