BACKGROUND Temsirolimus is an i.v. administered inhibitor of mammalian target of rapamycin with activity in the first-line setting in poor-prognosis patients with metastatic renal cell carcinoma (RCC). The efficacy of this agent after failure of prior inhibitors of vascular endothelial growth factor (VEGF) is unknown. METHODS a retrospective review of patients with metastatic RCC treated at the Cleveland Clinic Taussig Cancer Institute and three regional cancer centers in Ontario, Canada, through the Torisel (temsirolimus) Compassionate Use Program was conducted. Demographic, toxicity and response data were collected. RESULTS a total of 87 patients with metastatic RCC were identified who had previously been treated with inhibitors of VEGF subsequently treated with temsirolimus. The majority of patients had either intermediate or poor-prognosis disease at baseline. Expected toxic effects including hyperglycemia and noninfectious pneumonitis were observed. The RECIST-defined objective response rate was 5% and the stable disease rate was 65%. The median time to progression (TTP) was 3.9 months (95% confidence interval 2.8-4.8 months), and median overall survival was 11.2 months. CONCLUSIONS in a cohort of pre-treated intermediate to poor-prognosis patients with metastatic RCC, weekly i.v. temsirolimus is associated with predictable, but manageable toxicity, and a TTP approaching 4 months.