5-Methoxytryptamine and L-tryptophan methyl ester were acylated with malonic acid, dimethyl malonate, or succinic anhydride to produce the corresponding N,N'-dicarbonyltryptamine derivatives. The analgesic activity was evaluated by the tail flick test. All of the compounds exhibited desirable analgesic potency. This result is consistent with that of N-(N-acetyl-L-tryptophanyl)-5-methoxytryptamine and confirmed that introducing substituted tryptamine into the amide chain of melatonin does enhance analgesic potency.