This monograph summarizes 3 recent clinical trials and the worldwide clinical experience with Mahonia aquifolium in patients with psoriasis. Study 1 was an open-label study to evaluate the safety of Mahonia aquifolium in 39 patients treated for 12 weeks. Assessments made were modified PASI, global assessment, psoriasis history questionnaire, Dermatology Life Quality Index, and Psoriasis Disability Index. The results indicate statistically significant improvement in PASI score and Dermatology Life Quality Index after 4 weeks of treatment. This response continued 1 month after the end of treatment. Study 2 was a clinical trial of 32 patients with mild to moderate bilateral psoriasis treated up to 6 months. One side of the body received Mahonia and the other standard psoriatic treatment (eg, Dovonex cream). The primary outcomes were patient ratings of the Mahonia-treated side alone and the comparison between treatments received on each side of their body. Eighty-four percent of patients rated the Mahonia-treated psoriasis as good to excellent response. When compared with standard treatment, 63% of patients rated Mahonia aquifolium equal to or better than the standard psoriatic treatment. Study 3 was an observational study of 33 patients with mild to moderate bilateral psoriasis treated for 1 month. The results indicate improvement in psoriasis after 1 week of treatment. The side treated with Mahonia did as well or better than the side treated with the vehicle cream. Results from these 3 open-label clinical trials are in agreement with published data that include placebo-controlled studies. Taken together, these clinical studies conducted by several investigators in several countries indicate that Mahonia aquifolium is a safe and effective treatment of patients with mild to moderate psoriasis.