Biopsy specimens from patients with psoriasis concomitant with chronic opisthorchiasis were examined. Severe clinical course of combined disease was associated with degenerative changes in epidermocytes, keratinization disorders, and diffuse inflammatory cell infiltration of the derma. Combined therapy including anthelmintic agents produced a positive effect: decreased the degree of acanthosis, increased intracellular regeneration of epidermocytes, and suppressed inflammatory reaction of the derma and hyperplasia of immunocompetent cells. These data attested to an important role of opisthorchiasis in the pathogenesis of psoriatic disease.