This review illustrates that UVB phototherapy is not only a time-honored treatment, but also highly effective for widespread psoriasis. Treatment parameters include the frequency of irradiation, initial dose based on skin type or MED, increments of UV exposure, and maintenance schedule, according to defined protocols. UVB can be combined with adjunctive topical or systemic therapies either concomitantly or sequentially for additive effect. The use of various therapeutic modalities, including UVB phototherapy on a rotational basis, has been advocated for long-term control with reduced toxicity. UVB with emollients in an erythemogenic dosage schedule is as effective as PUVA for clearing of psoriasis in selected fair-skinned patients. Unlike PUVA, it does not involve a systemic photosensitizing drug and is relatively convenient and simple to use. UVB is the most commonly used therapy by dermatologists for widespread psoriasis that does not respond to topical therapies; it has been shown to be one of the most cost-effective therapies for widespread psoriasis.