Long-term followup of asymptomatic microhematuria. We present a 10 to 20-year followup assessment of 191 patients with unexplained microhematuria (including persons with insignificant lesions). Genitourinary malignancies did not develop in any of the patients (128 alive and 27 dead) evaluated after the first diagnostic investigation. Patient and physician compliance with followup protocols was poor. We currently recommend renal ultrasound and cystoscopy for the first diagnostic survey, have abandoned routine periodic studies and advise diagnostic studies only for patients in whom symptoms develop. 