We evaluated US, CT, intravenous urography, arteriography, retrograde pyelography and urine cytology results in a series of 23 patients with renal pelvic transitional-cell carcinomas, 14 of whom underwent US, 17 i.v. urography, 8 CT, 15 arteriography, 9 retrograde pyelography, and 17 patients urine cytology. A tumour was identified in 5 patients (36%) at US, in 11 patients (61%) at urography, in 7 (88%) at CT, in 10 patients (67%) at arteriography, and in 8 (89%) at retrograde pyelography. Urine cytology was assessed as showing changes consistent with Papanicolaou class III-V in 15 (88%) of 17 patients. When renal pelvic cancer is suspected, intravenous urography should be performed as the initial radiological examination and followed by CT, which may also identify tumour spread. Arteriography and retrograde pyelography are sometimes complementary investigations. Repeated urinary cytology is mandatory. Our results show that US alone is unreliable in detecting renal pelvic cancer.