Interleukin-6 (IL-6) production and proliferative responses by draining lymph node cells were studied in mice exposed topically to a series of chemicals. Chemicals with the capacity to induce sensitisation, but not non-sensitisers, promoted both IL-6 production and lymph node cell proliferation ex vivo. The responses exhibited similar kinetics, were dependent upon the dose of topically applied allergen, and correlated significantly. We demonstrate that the main source of IL-6 within draining lymph nodes is not proliferating T lymphocytes. The induction of a strong IL-6 response, and the relationship of this to cellular proliferation indicate that production of this cytokine within the lymph node is closely associated with the induction of contact sensitivity in mice.