The synchronous application of narrowband UVB phototherapy with 311 nm lamps (Philips TL-01) and bathing in Dead Sea salt solution was evaluated in a multicentre trial (n = 60) in outpatients suffering from psoriasis vulgaris. The study design consisted of an initial therapy phase of up to 35 treatments (three to five times a week) followed by maintenance therapy with up to 35 further applications (once or twice a week). Evaluation was performed separately for patients in according-to-protocol (ATP) (n = 280) and intention-to-treat (ITT) (n = 692) groups. An overall significant improvement of the Psoriasis Area and Severity Index (PASI) score (P < 0.05) could be shown for both groups during initial therapy with 71.4% improvement for ATP and 61% for ITT patients. The mean PASI for ATP (values for ITT in parentheses) was 17.7 (18.6) at baseline, 9.5 (10.7) after 20 applications and 5.2 (7.4) at the end of initial therapy. On average, ATP patients received 3.9 (3.5) applications per week with a cumulative irradiation dose of 19.5 J cm-2 (16.2 J cm-2). The most frequent side-effect was erythema, observed in 8.7% of the patients. Subjective evaluation of the therapy by the patients (n = 168) was excellent. Seventy-nine per cent of patients preferred the new treatment strategy in comparison with other previous therapies and 88% regarded this therapy as pleasant and comfortable. In conclusion, we could demonstrate a significant effect of therapy in both the ATP and the ITT groups for this new treatment system which imitates, as far as possible, the Dead Sea climatic conditions, with no severe side-effects and a high acceptance by the patients.