We synthetized pyridobenzoxazocynone that differs in the enlarged eight-membered heterocyclic system from the basic structure of pyridobenzoxazepinones a known class of non-nucleoside HIV-1 reverse transcriptase inhibitors. Pyridobenzoxazocynone hydrochloride was found to inhibit HIV-1 reverse transcriptase activity. At concentration 0.35 microM the enzyme activity decreased by 64 +/- 14%. Higher concentrations of pyridobenzoxazocynone hydrochloride completely abolished the enzyme activity expressed as radioactivity of acid insoluble products. These results suggest that pyridobenzoxazocynones may represent a new class of HIV-1 reverse transcriptase inhibitors.