Psoriasis is an inherited condition that may require specific environmental factors to become activated; immunological factors are clearly important in pathogenesis. Psoriasis is incurable and characterised by exacerbations and remissions, but much can be done to relieve symptoms. Diagnosis relies on clinical features, particularly the characteristic appearance and history of the lesions. Management needs to address both medical and psychological aspects and to be flexible in response to changes in the condition and in patient needs. Choice of treatment should proceed stepwise, with general measures and topical therapy first, phototherapy second and oral therapy last. Topical therapy includes tars, dithranol and topical corticosteroids. Oral therapy includes methotrexate, acitretin, cyclosporin and propylthiouracil. Combination therapy is often needed and rotation of therapies is critical; rigid adherence to one line of therapy is usually inappropriate.