Phorbol 12-myristate 13-acetate (PMA) is a specific activator of group A (α, βI, βII, γ) and group B (δ, ε, η, θ) Protein Kinase Cs (PKCs) (in the 1–100nM range). Phorbol esters, such as PMA, affect PKCs by mimicking diacylglycerol, a natural ligand and activator of PKCs. PMA is an effective skin irritant and potent tumor promoter in mice. A common alternative name for PMA is 12-O-tetradecanoylphorbol 13-acetate (TPA). The chemical identity and purity of PMA are confirmed by proton NMR.