The present invention provides methods of treating or preventing autoimmune diseases with 2,4-pyrimidinediamine compounds, as well as methods of treating, preventing or ameliorating symptoms associated with such diseases. Specific examples of autoimmune diseases that can be treated or prevented with the compounds include rheumatoid arthritis and/or its associated symptoms, systemic lups erythematosis and/or its associated symptoms and multiple sclerosis and/or its associated symptoms.