The usefulness of real-time ultrasonography as a guidance method in performing percutaneous renal biopsy is evaluated on the basis of a series of 114 patients with diffuse nephropathies. Sufficient renal tissue for light microscopy was obtained in 102 patients (89.5%) and enough for electron microscopy in 93 patients (81.6%) and for fluorescence microscopy in 91 patients (79.8%). A final histological diagnosis was possible in 106 patients (93%). The high diagnostic rate, the reduction in the contraindications to the procedure, the lack of major postbiopsy complications, and the cost effectiveness probably make realtime ultrasound scanning the method of choice when performing renal biopsy in patients with diffuse nephropathies.