Background: Psoralen-UVA (PUVA) photochemotherapy is widely used for the treatment of psoriasis despite concerns of skin carcinogenesis from high cumulative UVA doses and number of treatments. Objective: We attempted to determine whether combined bath-PUVA with narrow-band (311 nm) phototherapy improves efficacy and reduces long-term toxicity. Methods: Twelve psoriatic patients underwent phototesting with 311 nm lamps and, after topical bath-water psoralen sensitization, with 311 nm, UVA, or both radiations. Patients were treated with bath-PUVA on one side of the body and with bath-PUVA plus 311 nm exposures (bath-PUVA–311 nm) on the other side. On both sides, four weekly treatments were delivered and UVA doses were increased once weekly whereas 311 nm doses were adjusted at each exposure. Results: Psoralen sensitization did not modify the erythematous threshold to 311 nm radiation. However, 311 nm exposures enhanced the phototoxic activity of bath-PUVA. Bath-PUVA–311 nm cleared psoriasis with fewer exposures and lower cumulative UVA doses under the same minimally erythemogenic conditions. Conclusion: Combination with 311 nm exposures enhanced the phototoxic and therapeutic activities of bath-PUVA. (J Am Acad Dermatol 1998;38:687-90.)