Galectin-3 (gal-3) is a glycoprotein involved in various physiological cellular processes. Altered expression/loss of function of gal-3 is suggested to be involved in the pathogenesis and further progression of various human cancer entities. The aim of the present investigation was to elucidate the role of galectin-3 in the development and/or progression of non-muscle invasive (pTa, pT1) transitional cell carcinoma (TCC) of the urinary bladder. Gal-3 was analyzed by immunohistochemistry in 162 randomly selected non-muscle invasive bladder cancer specimens (pTa, 91; pT1, 71) using tissue microarray technique. It was compared with various patient and tumour characteristics (t-test). In addition, the role of gal-3 in association with tumour recurrence and progression was investigated (Log-rank test, Cox regression analysis). Gal-3 was found to be negatively correlated with tumour grade (p<0.02). Within the group of non-muscle invasive TCC, gal-3 could not differentiate between pTa and pT1 tumours (p=0.50), and within the subgroup of pTa tumours, loss of gal-3 determined the likelihood for the development of recurrent disease (p<0.03; Student's t-test). Furthermore, as demonstrated by Kaplan-Meier analysis, the expression level of gal-3 was identified to predict the duration of recurrence-free survival (p=0.01). In the multivariate analysis, gal-3 was found as an independent prognostic marker for predicting recurrence among the cohort of bladder tumours classified as pTa. In conclusion, loss of galectin-3 appears to be involved in the carcinogenesis of TCC and to serve as a valuable biological variable to identify a subgroup of Ta bladder cancer patients at high risk for the development of recurrent disease.