It is hypothesized that the balance of cytokines produced by Th1/Th2 subsets of T helper cells plays an important role in the development of autoimmune diseases. Murine collagen‐induced arthritis (CIA) is an example of an autoimmune disease in which immunization with cartilage‐derived type II collagen induces, firstly, a T cell response to type II collagen and, secondly, the manifestation of a destructive inflammatory response in affected joints. We have investigated the role of Th1/Th2 responses in the development of CIA by monitoring levels of interferon (IFN)‐γ (a Th1 cytokine) and interleukin (IL)‐4 and IL‐10 (Th2 cytokines), and IL‐1β and tumor necrosis factor (TNF) (pro‐inflammatory cytokines) produced by cultured draining lymph node cells (LNC) from collagen‐immunized DBA/1 mice during the induction phase of arthritis and throughout the time of clinical manifestation and subsequent remission of the disease. Although a transient increase in IL‐10 was detected 3 days after immunization, Th2 cytokine production was found to be almost completely suppressed 6 days after immunization. In contrast, IFN‐γ was detected in LNC cultures as early as 6 days after immunization and the addition of type II collagen to the culture medium resulted in an approximately 10‐fold increase in IFN‐γ production, indicating that a predominantly Th1 response had become established by this time. IFN‐γ production by LNC was found to be further increased at the time of clinical manifestation of arthritis and could be up‐regulated by co‐culture with type II collagen. IL‐10 was not detected in LNC cultures at the onset of arthritis and IL‐4, although present, was found to be markedly suppressed in LNC cultures containing type II collagen. These findings indicate that Th1 responses are predominant at the time of onset of arthritis and that the activation of collagen‐specific Th1 cells may result in suppression of Th2 activity. IFN‐γ production declined progressively during the progression and subsequent remission of arthritis whereas levels of IL‐10 increased and low, though persistent, levels of IL‐4 were detected throughout this period. High levels of IL‐1β and TNF‐α production were detected at the onset of the disease. The role of Th1 responses in the development of CIA was further emphasized by the observation that immunization of mice with type II collagen in incomplete Freund's adjuvant, which normally fails to induce arthritis, resulted in a predominantly Th2 cytokine profile.