A combination of histologic and barium perfusion-microangiographic methods have been employed to correlate cytologic and microangiographic characteristics of Streptozotocin-induced renal tumors in rats. Four of 11 rats developed renal tumors within six to seven months following Streptozotocin administration. A total of twelve tumors was found in these animals. The neoplasms displayed a continuum of benign and malignant cytologic characteristics and varied considerably in extent of vascularity, as seen on microangiography. One tumor appeared locally invasive beyond the confines of its pseudo-capsule. Microangiography depicted well the microvascular features of these tumors and correlated closely with the histologic findings.