Chemical investigation of the tubers of Corydalis ternata resulted in the isolation and characterization of four new benzylisoquinoline alkaloids, epi-coryximine (1) and coryternatines A-C (2-4), along with 10 known alkaloids (5-14). Their structures were established on the basis of extensive spectroscopic data analyses and comparison with spectroscopic data reported. In addition, the cytotoxicities of the alkaloids (1-14) were evaluated by determining their inhibitory effects on several human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15) using the SRB assay. Compound 8 showed significant cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines (IC(50)=8.34, 5.14, 7.87, and 2.86 microM, respectively). The four new compounds (1-4) exhibited selective cytotoxicity against the HCT-15 cell line.