Background: IL-2 is a T-cell growth factor tested in a variety of regimens for advanced melanoma (MEL) and renal cell carcinoma (RCC). High-dose IL-2 (600,000-720,000 IU/kg administered intravenously every 8 hours for up to 14 consecutive doses) was approved by FDA for advanced MEL and RCC in 1998 based upon the durability of responses observed. Early studies of HD IL-2 reported overall (OR) and complete response (CR) rates of 16% and 8% respectively. Severe toxicity limited use to specialized centers with standardized protocols, either intensive care (ICU) or oncology specialty settings. The U Pittsburgh has treated 1022 patients with IL-2 at any dosage and we here present outcomes of 550 MEL pts treated with HD IL-2 in an oncology specialty non-ICU setting. Methods: Clinical and radiological data were collected on all pts treated with IL-2 using the UPCI Cancer Registry and Medical Archival System (MARS). Pharmacy records were reviewed for dosing details. The influence of baseline characteristics on treatment outcomes was assessed using Cox proportional hazards analysis. Results: A total of 848 pts received HD IL-2, of which 298 pts had RCC while 550 had MEL. Detailed pharmacy dosing records were reviewed from 176 pts treated over the past 12 years (2000-2012) who received a total of 3738 cycles. Of 165 pts evaluable for response, OR was documented in 24 pts (14.8%) and CR in 5 pts (3.0%). Median overall survival (OS) was 10.0 mos for all patients and 21.5 mos for responders (CR+PR). Median number of doses per cycle was 7. Toxicity was consistent with prior reports. HD IL-2 required ICU transfers in 5% and 1 death was attributed to HD IL-2. Pts with higher baseline lactate dehydrogenase (LDH) had poorer OS (p < 0.05). Conclusions: In this large and uniformly treated series of recent patients treated with IL-2 OR/CR rates with HD IL-2 are 14.8% and 3.0% respectively. Higher LDH is associated with poorer outcome. Biomarkers of response are currently being evaluated in banked clinical specimens collected from patients under the SPORE in Skin Cancer (P50 CA121973).