Abstract: 7α-bis (β-chloroethyl) aminomethyl-6, 14-endoetheno-tetrahydro oripavine (a-CAM) is a new irreversible opioid receptor agonist. Its effect on isolated tissues (guinea pig ileum, mouse vas deferens, rat vas deferens and rabbit vas deferens) were studied. It was shown to be bound irreversibly to rat brain P₂ membrane preparations. The ED₅₀ of its analgesic effect in mice (icy) was found to be 0.12 nmol/mouse, and the effect may last as long as 2～3 days. It is a compound which produces the longest analgesia known up to date. A single dose (icy) of a-CAM was sufficient to produce dependence in mice. Thus, the compound may serve as an agent for studying the mechanism of physical dependence.