Six bioactive alkaloids, aristolactam B(1), poperolactam A(2), aristolactam A(3), norcepharadione B(4), cepharadione B(5) and splendidine(6) were isolated by bioactivity-guided fractionalton of a methanolic extract of the aerial part of Houttuynia cordata. Several of them exhibited significant cytotoxicity against five human tumor cell lines (A-549,SK-OV-3,SK-MEL-2, XF-498 and HCT-15) in vitro.