Goeckerman's therapy of psoriasis combines exposure to pharmaceutical coal tar and UV-B radiation. In the pilot study (15 patients had been diagnosed with psoriasis, the average time period in hospital therapy was 24 days, the average age of the patients was 29 years, 47% of them were smokers) a level of genotoxic risk from therapy was evaluated by using chromosomal aberration of peripheral lymphocytes. The study suggested the presence of an increased genotoxic risk from the therapy. The PASI scores (Psoriasis Area and Severity Index) were monitored.