We found that indolicidin, a natural antimicrobial peptide, has HIV-1 integrase inhibitory activity. Subsequently, we also discovered analogs of indolicidin with substantially higher inhibitory potency. The dimers and tetramers of the most active sequence (ILPWKWPWWPWPP) were prepared by connection of the monomers' C-terminal ends, using lysine as a linker. The inhibitory potency of the dimeric peptide is higher than the monomeric peptide. The tetrameric peptide, prepared by connection of two dimers at C-ends using again lysine as the linker, is the most potent integrase inhibitor with IC(50) value of 0.6 microM for both 3'-end processing and strand transfer.