The effectiveness of the long wavelength ultraviolet therapy (UVA-1) in complex treatment of patients with psoriasis has been studied during the research. There 20 patients with moderately severe and severe psoriasis in the phase of progressive dermatosis have been observed. The therapy was organized using photobox Waldmann UV-7001K (Herbert Waldmann GmbH & Co, Germany) and F85 \ 100W-TL10R lamps, creating radiation spectrum of UVA-1 (ƛ = 340 – 400 nm) and emission maximum was ƛ=370 nm. 20 patients of the comparison group receive standard therapy in combination with PUVA therapy. The group did not differ from the main group of patients in age, duration and form of the disease. The effectiveness of the treatment was measured according to the dynamic assessment of PASI index. The usage of a long wavelength ultraviolet therapy (UVA-1) has caused a reduction of the severity and the extent of skin lesions, gave positive outcomes in all patients of the study. No adverse effects caused by the therapy undertaken have been noted. The administration of long wavelength ultraviolet therapy (UVA-1) is safe and effective in patients with psoriasis.