The efficacy of trimethylpsoralen bath PUVA and UVB TL01 were compared in chronic plaque psoriasis. Patients were randomly assigned to receive UVB TL01 on one side and bath PUVA on the contra-lateral side. Altogether 17 patients received treatments and 15 completed the trial. The decrease in the PASI score was greater with UVB TL01 than PUVA. At the end of the treatment period, the difference was highly significant (p < 0.001). The difference was already significant at week 3 (p = 0.014). The relative median decrease in the PASI score was 77% (24-100%) with UVB and 45% (8-100%) with PUVA. The median cumulative UVB dose was 39.92 (range 13.95-81.56) J/cm2 and the corresponding UVA dose was 8.06 (range 3.31-12.51) J/cm2. All patients relapsed within 4 months. Narrowband UVB improved psoriasis clinically and statistically more efficiently than trimethylpsoralen bath PUVA, and UVB was better tolerated.