An anti-HIV agent containing, as an active ingredient, a 4-oxoquinoline compound represented by the following formula [I] ##STR00001## wherein each symbol is as defined in the specification, or a pharmaceutically acceptable salt thereof. The compound of the present invention has HIV integrase inhibitory action and is useful as an anti-HIV agent for the prophylaxis or therapy of AIDS. Moreover, by a combined use with other anti-HIV agents such as protease inhibitors, reverse transcriptase inhibitors and the like, the compound can become a more effective anti-HIV agent. Since the compound has high inhibitory activity specific for integrases, it can provide a safe pharmaceutical agent with a fewer side effects for human.