Patients with psoriasis frequently use preparations of plant extracts. Physicians need to be aware of the current evidence concerning these products. This review evaluates the efficacy and safety of preparations of plant extracts used topically for psoriasis. Searches were conducted in PubMed, Embase, the Cochrane library, two Chinese databases and article reference lists. Randomized controlled trials investigating extracts of single plants were included. Preparations of multiple plants and combinations of plant extracts plus conventional therapies were excluded. Two authors conducted searches, extracted data and assessed risk of bias. Outcomes used in meta-analyses were: clinical efficacy, Psoriasis Area and Severity Index score, and quality of life and symptom scores. The 12 included studies investigated extracts of: Mahonia aquifolium (n = 5), Aloe vera (n = 3), indigo naturalis (n = 2), kukui nut oil (n = 1) and Camptotheca acuminata nut (n = 1). Methodological quality was variable. Six studies provided data suitable for meta-analysis of clinical efficacy, and five were vs. placebo (relative risk 3·37, 95% confidence interval 1·36-8·33). Experimental studies indicate components of indigo naturalis, Mahonia and Camptotheca have anti-inflammatory, antiproliferative and other actions of relevance to psoriasis. The clinical trial evidence provides limited support for preparations containing extracts of M. aquifolium, indigo naturalis and Aloe vera for the topical management of plaque psoriasis based on multiple studies. No serious adverse events were reported. Because of the small size of most studies and methodological weaknesses, strong conclusions cannot be made. The magnitudes of any effects cannot be measured with accuracy, so it is difficult to assess the clinical relevance of these preparations.