Purpose To evaluate the efficacy, safety, and pharmacokinetics of multiple doses of CCI-779, a novel mammalian target of rapamycin kinase inhibitor, in patients with advanced refractory renal cell carcinoma (RCC). Patients and methods Patients ( n = 111) were randomly assigned to receive 25, 75, or 250 mg CCI-779 weekly as a 30-minute intravenous infusion. Patients were evaluated for tumor response, time to tumor progression, survival, and adverse events. Blood samples were collected to determine CCI-779 pharmacokinetics. Results CCI-779 produced an objective response rate of 7% (one complete response and seven partial responses) and minor responses in 26% of these advanced RCC patients. Median time to tumor progression was 5.8 months and median survival was 15.0 months. The most frequently occurring CCI-779-related adverse events of all grades were maculopapular rash (76%), mucositis (70%), asthenia (50%), and nausea (43%). The most frequently occurring grade 3 or 4 adverse events were hyperglycemia (17%), hypophosphatemia (13%), anemia (9%), and hypertriglyceridemia (6%). Neither toxicity nor efficacy was significantly influenced by CCI-779 dose level. Patients were retrospectively classified into good-, intermediate-, or poor-risk groups on the basis of criteria used by Motzer et al for a first-line metastatic RCC population treated with interferon-alfa. Within each risk group, the median survivals of patients at each dose level were similar. Conclusion In patients with advanced RCC, CCI-779 showed antitumor activity and encouraging survival and was generally well tolerated over the three dose levels tested.