Psoriasis is a chronic, recurrent disease that affects between 1% and 3% of the population. Patients with moderate to severe disease generally require phototherapy (e.g. narrowband ultraviolet B radiation), photochemotherapy (oral psoralen plus ultraviolet A radiation) or systemic agents (e.g. ciclosporin, methotrexate, oral retinoids, fumaric acid esters) to control their disease adequately. In general, these therapeutic modalities have proven to be highly effective in the treatment of psoriasis. However, potentially serious toxicities can limit their long-term use. Given that there is no standard therapeutic approach for patients with moderate to severe psoriasis, the benefits and risks of phototherapy, photochemotherapy and systemic therapy must be weighed carefully for each patient, and treatment individualized accordingly. This review summarizes the benefits and risks of traditional, nonbiological therapies for moderate to severe chronic plaque psoriasis.