We examined the activity of PLA2 by quick simple trace titration method in the serum and cutaneous tissues in patients with psoriasis vulgaris patients than that in the control group. The activity of PLA2 was significantly higher in psoriasis vulgaris patients than that in the control group. PLA2 activity in sera of psoriasis patients in the active stage or rash area > 30% was higher than that in the inactive stage or rash area < 30%. It is suggested that the sera PLA2 activity may be related to the disease activity in patients with psoriasis vulgaris, and PLA2 may play an important role in the pathogenesis of the psoriasis.