Bacillus Calmette Guerin (BCG) has been the mainstay of intravesical treatment, however, its clinical effectiveness is accompanied by a wide range of adverse events. Gemcitabine has a good safety profile with promising features for the use against intermediate risk non-muscle invasive bladder cancer (NMIBC). It can be a potential chemotherapeutic drug for high- risk patients. The aim of this study was to evaluate the safety and efficacy of adjuvant intravesical gemcitabine versus BCG in the treatment of intermediate and high -risk NMIBC. Patients and methods: Between May 2006 and April 2008, a total of 57 patients were randomized into 2 groups; group I: 28 patients, were treated with six weekly intravesical instillation of BCG and group II: 29 patients, received six weekly intravesical grmcitabine. Patients were evaluated for response, at 8 weeks, then every 3 months. Outcome measures were response rate, overall recurrence rate, progression rate, median recurrence free period, median progression free period and 1-year recurrence free survival. Treatment related complications were also evaluated. Results: For intermediate risk patients, there was no significant difference between the two groups in the complete response (CR) rate (93.3% vs. 87.5%), the overall recurrence rate (33.3%vs.25%), the progression rate (6.7% vs. 6.2%), and the median progression free period (13 vs. 16 months). However, the median recurrence free period was longer for group I compared to group II (18.5 vs. 15 months) and the difference was statistically significant. Kaplan-Meier curve showed that there was no significant difference between the two groups in the 1-year recurrence free survival (95.3% vs. 98.7%) and the median recurrence free survival (22 vs.18 months). For high risk patients there was no significant difference between the 2groups in CR rate (61.5% vs. 76.9%), the progression rate (15.4% for both groups) the median recurrence free period (15 vs. 14 months) and the median progression free period (17 vs. 15 months). However, the overall recurrence rate of group I was lower than that of group II (7.7% vs. 30.8%) and the difference was statistically significant. Kaplan-Meier curve showed that there was no significant difference between the two groups in the 1-year recurrence free survival (76.9% vs. 69.2%) and the median recurrence free survival (18 vs.15 months). The adverse events of group I were more marked than that of group II. Conclusion: Gemcitabine is active and well tolerated for intravesical instillation.It is considered to be an efficient treatment for intermediate risk NMIBC. However, for high- risk group, it is inferior to BCG, but owing to its favorable toxicity profile, it may be useful for patients intolerant to BCG. [