Expression of cyclooxygenase-2 and uroplakins in prediction of recurrence of non-muscle invasive urothelial carcinoma of the urinary bladder. Objectives: The aim of this research was to determine predictive value of cyclooxygenase-2 (COX-2) and uroplakin III (UPIII) expression in recurrence of solitary papillary non-muscle invasive carcinoma of the urinary bladder (NMICUB) and its connection with tumour infiltrating lymphocytes (TILs). Patients and Methods: In the period from 1996 to 2006 the specimens of the urinary bladder tumours were obtained with transurethral resection (TUR) at the Department of Urology of the University Hospital Rijeka and analyzed at the Department of Pathology of the Faculty of Medicine in Rijeka. Among these specimens there were 127 of them taken from solitary tumours and diagnosed as NMICUB. None of the patients received any other form of adjuvant therapy or treatment after the initial TUR. The immunohistochemical staining of the specimen tissue microarrays was applied using the antibodies Uroplakin III – clone AU-1 and COX-2 – clone 4H12 and the immunohistochemical expression was quantified and scored as weak, intermediate and strong. All the tumours were classified as either papillary urothelial neoplasm of low malignant potential or low-grade papillary urothelial carcinoma. During the first 5 post-operative years, and ≥ 6 months after the initial operation, 78 patients developed recurrent disease and 49 patients did not. The presence of TILs was assessed and classified as absent or present. Results: The COX-2 and UPIII expression as well as TILs were detected in most of the NMICUB patients and they did not differ greatly in relation to the very size of tumour and stage of disease. The recurrence of disease was connected with neither age nor gender of the patients, while pathology and staging of disease differed between recurrent and non-recurrent cases. Lower COX-2 expression and poor presence of TILs were associated with recurrence of the disease, while UPIII expression did not differ significantly between recurrent and non-recurrent patients. Negative correlation of COX-2 and UPIII was found in non-recurrent patients. Negative correlation of COX-2 and TILs was found in recurrent group of patients. TILs were significant negative predictor of recurrence. Conclusion: Tumours with low UPIII expression will probably not recur if having the COX-2 overexpression. Tumours that are likely to recur and having low UPIII expression are, at the same time, most probably connected with absence of TILs. Patients with lower COX-2 expression and absence of TILs in NMIBC should be followed up more vigorously, and some of these patients will probably be selected for adjuvant therapy.