The invention provides mebendazole for use in the treatment or prophylaxis of a chronic inflammatory disease, and in particular wherein the chronic inflammatory disease is an autoimmune disease, for example sarcoidosis, systemic lupus erythematosus (SLE), Huntington's disease, end stage renal disease, systemic sclerosis (also called scleroderma), myositis, diabetes type 1, multiple sclerosis, Sjögren's syndrome, rheumatoid arthritis, psoriasis, primary biliary cirrhosis, autoimmune hepatitis, Graves' disease, Addison's disease, tuberculosis, Crohn's disease, ulcerative colitis, inflammatory bowel disease, Alzheimer's disease and coeliac disease. A method for the treatment or prophylaxis of a chronic inflammatory disease, comprising administering an effective amount of a mebendazole or a pharmaceutical composition of mebendazole is also provided. The use of mebendazole for the manufacture of a medicament for the treatment of a chronic inflammatory disease is also provided.