4596 Background: Non-transitional carcinomas account for less than 5% of all malignant neoplasms of the bladder and upper urinary tract in Europe and USA. There have been reports suggesting a worse outcome of non-transitional carcinomas following cystectomy, but there is limited information regarding the benefit from systemic chemotherapy in this population. We, therefore, analysed the efficacy of platinum-based chemotherapy in patients with pure squamous or mixed carcinomas who had been entered into our database and we compared it with that in pure transitional carcinomas. Methods: 404 consecutive patients with advanced cancer were included in this analysis. All patients had been treated with cisplatin or carboplatin-based chemotherapy within the context of 5 studies. 25 patients (6.2%) had mixed histology (transitional + squamous: 24, transitional + sarcomatoid: 1) and 17 patients (4.2%) had pure squamous carcinoma. Results: There were no statistically significant differences in baseline characteristics (sex, PS, haemoglobin, weight loss, sites of metastases), although there was a trend for more frequent distant metastases in non-pure transitional carcinomas (mixed 60%, squamous 70%, pure transitional 48%, p=0,122). Median follow up of living patients was 39.2 months. Objective response rates did not differ significantly according to histology (mixed 32%, squamous 35%, pure transitional 44%, p=0,381). Median survival of mixed carcinomas was 9 months, squamous carcinomas 16.6 months and pure transitional 11 months (p=0.386).Univariate analysis of baseline characteristics showed that ECOG PS 2 or 3 and hemoglobin < 10 were associated with worse prognosis in mixed histology (p<0.0001 and p=0.005), while hemoglobin < 10 was also an adverse prognostic factor in squamous carcinomas (p=0.09). Conclusions: Non-transitional histology does not predict for an inferior outcome after platinum-based chemotherapy for advanced urothelial carcinoma. Well known prognostic factors in transitional cell carcinomas (PS and baseline haemoglobin) were also associated with prognosis in mixed and squamous cell carcinomas. No significant financial relationships to disclose.