Neoplastic diseases of the kidneys and urinary collecting system are relatively common, but when detected early, they have an excellent prognosis. Because gross or microscopic hematuria may be an early harbinger of genitourinary pathology, the primary care physician and internist play an integral role in diagnosing these diseases. A high index of suspicion together with a thorough history, physical examination, and appropriate diagnostic studies will enable the correct diagnosis and improved patient management in most cases.