We report the use of non-invasive tape stripping to sample psoriatic lesional and non-lesional skin in 96 patients. The procedure was well tolerated with any discomfort described as mild; we did not observe any cases of Koebner phenomena at any non-lesional tape-stripped sites. Tape-harvested epidermis was extracted for RNA, which was profiled by semiquantitative reverse transcriptase-PCR. This analysis revealed that mRNAs for tumor necrosis factor alpha, IFNgamma, Krt-16, CD2, IL-23A, IL-12B, and vascular endothelial growth factor are overexpressed in the "average" psoriatic lesion in a majority of patients. In addition, 10 of these patients were biopsied at lesional and non-lesional sites and the expression data compared to tape-stripping data. This comparison shows that five of seven mRNA are more highly expressed in cells captured by tape stripping than biopsy, suggesting that the upper aspect of a lesion contains cells very active in the disease. The tape-harvesting data reveal that approximately 46% of lesions have at least one pathogenic mRNA within non-lesional skin limits. Data demonstrate that tape stripping reveals mRNA markers not detected in biopsy samples and thus the method may be a useful supplement to biopsy.