HER2/neu is a defective transmembrane tyrosine kinase receptor, homologue to the epidermal growth factor receptor, showing overexpression in a large variety of tumor cells. There are no studies published so far regarding HER2/neu overexpression and sensitivity of the urothelial tumors of the urinary bladder to anti-HER2/neu therapy. There are a relatively high number of articles in the literature referring to HER2/neu expression in urothelial tumors of the urinary bladder, but only two of them had investigated HER2/neu expression in patients with urothelial tumors of the upper urinary tract. We have studied HER2/neu overexpression in 59 patients with urothelial carcinomas of the urinary tract by immunohistochemistry. Normal urothelium and the elements of the neighboring renal parenchyma were negative. Out of the 59 cases of urothelial carcinomas, 38 were negative (0 and +1) and 21 were positive: eight were moderately and 13 were intensely positive (+2 and +3). The percentage of positive cases was 35.59%. The negative cases were mostly well-differentiated, G1 tumors, no matter the T-tumor stage. Most of the cases were diagnosed as papillary or, rarely, infiltrative. There is no correlation between HER2/neu overexpression and the tumor stage. The same was true for the lymph node status. The expression intensity, however, was significantly correlated with the differentiation grade. Overexpression was most likely present in tumors with high differentiation grade (p<0.05).