The sap of Euphorbia peplus, commonly know as 'petty spurge', 'radium weed' or 'milkweed' has been used for centuries as a traditional treatment for skin conditions, including warts, corns and cancers of the skin. Documentation of its use by medical professionals to treat basal cell carcinoma (BCC) dates from the early 19 century. Individuals who participated in a 1988 survey of home treatments for cancer indicated the sap of E. peplus was an effective cure for actinic lesions leading the investigators to suggest that this potential utility should be further explored in controlled clinical trials. The fractionation of the sap E. peplus using solvents of varying polarity yielded several macrocyclic diterpenes, many of which were found to have cytotoxic activity or the ability to influence cellular differentiation. Ultimately, ingenol 3-angelate (I3A) of PEP005, emerged as a promising potential new anti-cancer treatment. Here we report the proceedings from the First International Conference on PEP005, covering the exciting potential of PEP005 as the therapeutic agent for the treatment of skin cancer, leukemia and bladder cancer.