Four analogs of human β‐endorphin (βh‐EP) have been synthesized: [Gly31]‐βh‐EP‐Gly‐NH2, [CH3(CH2)4NH312]‐βh‐EP, [Gly31]‐βh‐EP‐Gly‐Gly‐NH2, and [Gln8, Gly31]‐βh‐EP‐Gly‐Gly‐NH2. All are more active than βh‐EP in an opiate receptor binding assay. Stepwise extension at the COOH‐terminus shows a progressive increase in binding activity. The last analog, which combines extension at the COOH‐terminus with elimination of the remaining anionic charge in βh‐EP, is nine times more active than the parent molecule.