A series of N-mustard-quinoline conjugates bearing a urea or hydrazinecarboxamide linker was synthesized for antitumor evaluation. The in vitro cytotoxicity studies revealed that compounds with hydrazinecarboxamide linkers were generally more cytotoxic than the corresponding urea counterparts in inhibiting human lymphoblastic leukemia and various solid tumor cell growths in culture. The therapeutic efficacy against human tumor xenografts in animal model was studied. It was shown that complete tumor remission in nude mice bearing human breast carcinoma MX-1 xenograft by 17a, i and 18c, d was achieved. In the present study, it was revealed that both linkers are able to lower the chemically reactive N-mustard pharmacophore and thus the newly synthesized conjugates possess a long half-life in rat plasma. Moreover, the new N-mustard derivatives are able to induce DNA cross-linking either by modified comet assay or by alkaline agarose gel shift assay.