The present study reports our experience in the management of 13 patients with trauma to previously asymptomatic pathological kidney (11.6% of 112 cases of renal trauma treated over the period 1980-1990). The diagnostic difficulties and treatments, which are unlike those of trauma to normal kidney, are discussed and the literature reviewed. Hydronephrosis from ureteropelvic junction stenosis was the preexisting pathology that was frequently diagnosed (41.6%), followed by trauma to kidney with tumor (30.7%). Twelve (92%) patients underwent surgery: 2 (15.3%) were emergency and the rest were elective surgery. One patient with hilar sinus cysts received medical treatment. Conservative surgery was performed in 5 renal units (1 with bilateral involvement) and nephrectomy was performed in 8 patients (65.1%). The kidney with a tumor is more compromised by the renal injury. Furthermore, post trauma contusion/laceration of the tumor may present problems relative to tumor stage.