['The sap from Euphorbia peplus, commonly known as petty spurge in the U.K. or radium weed in Australia, has been used as a traditional treatment for a number of cancers.', 'To determine the effectiveness of E. peplus sap in a phase I/II clinical study for the topical treatment of basal cell carcinomas (BCC), squamous cell carcinomas (SCC) and intraepidermal carcinomas (IEC).', 'Thirty-six patients, who had refused, failed or were unsuitable for conventional treatment, were enrolled in a phase I/II clinical study. A total of 48 skin cancer lesions were treated topically with 100-300 μL of E. peplus sap once daily for 3 days.', 'The complete clinical response rates at 1 month were 82% (n = 28) for BCC, 94% (n = 16) for IEC and 75% (n = 4) for SCC. After a mean follow-up of 15 months these rates were 57%, 75% and 50%, respectively. For superficial lesions < 16 mm, the response rates after follow-up were 100% for IEC (n = 10) and 78% for BCC (n = 9).'] Do the sap from Euphorbia peplus is effective against human nonmelanoma skin cancers?