An amino acid derivative and nitric oxide synthase (NOS) inhibitor with potential antineoplastic and antiangiogenic activities. Upon administration, NG-nitro-L-arginine inhibits the enzyme nitric oxide synthase, thereby preventing the formation of nitric oxide (NO). By preventing NO generation, the vasodilatory effects of NO are abrogated leading to vasoconstriction, reduction in vascular permeability and an inhibition of angiogenesis. As blood flow to tumors is restricted, this may result in an inhibition of tumor cell proliferation. NO plays an important role in tumor blood flow and stimulation of angiogenesis, tumor progression, survival, migration and invasiveness.