In 1991, a comprehensive review was published highlighting the importance of cytokines in the immunopathogenesis of psoriasis.1 Since then, many advances have been made regarding the critical role for pathogenic T cells as causing this common and enigmatic skin disease. While epidermal keratinocytes are clearly involved as participants in establishment of the appropriate cytokine milieu as presented earlier, more recent data point to T lymphocytes as triggering the chain reaction of cellular and molecular networks that culminate in the formation of a psoriatic plaque. In this review, 3 major topics will be addressed.