Background: T cell activation is discussed as an important factor in the pathogenesis of psoriasis. Recently, a lot of attention has been paid to the role of superantigens in T cell activation in the pathogenesis of psoriasis. In this study, the role of staphylococcal superantigens in the pathogenesis of psoriasis with identification of staphylococcal toxin levels in the skin lesions of patients with chronic plaque psoriasis has been studied. Method: In this case-control study, biopsies were taken from the skin of 40 patients with chronic plaque type psoriasis and 40 controls. Staphylococcal superantigens such as staphylococcus enterotoxin A, staphylococcus enterotoxin C, and toxic shock syndrome toxin 1 were investigated using polymerase chain reaction. Result: Staphylococcus aureus was isolated from 6.5% of the psoriasis patients and 2.5% of the individuals in the control group and all of them were toxin producer. There was a significant difference between controls and patients. Conclusion: Bacterial superantigens probably play an important role in the pathogenesis of chronic plaque type psoriasis.