Angiostatin is an inhibitor of angiogenesis, the process by which new blood vessels are formed from pre-existing ones. The fact that tumor growth and metastasis dissemination are angiogenesis-dependent processes has awakened interest in angiogenesis inhibitors as anticancer treatment drugs. Angiostatin, a potent angiogenesis inhibitor, is currently in phase I clinical trials. Human angiostatin containing the first three kringle domains of plasminogen (K1-3) has been crystallized and high-resolution data were collected. The crystals belong to the P4(1)2(1)2 space group, with unit-cell parameters a = b = 56.94, c = 192.97 A. A data set to a resolution of 1.75 A with an overall R(merge) and I/sigma(I) of 7% and 19.5, respectively, was obtained.