Background: Pathway crosstalk and emergence of drug resistance have limited the activity of targeted therapies, including anti-angiogenic agents and mTORC1 inhibitors. However, this vulnerability may be addressed by rationally combining targeted therapies to improve outcomes. We sought to determine the MTD/recommended phase II dose and define the pharmacokinetics (PK) of the combination of sorafenib (S), bevacizumab (B), and temsirolimus (T) in patients with advanced solid tumors. Methods: S was given once or twice daily, B was given intravenously every three weeks, and T was given intravenously weekly. Doses were escalated in a stair-step dose escalation with 6 planned dose levels (DL) in a standard 3+3 design. Responses were defined using RECIST 1.1. Results: To date, 51 patients have been enrolled. Three patients withdrew consent after only one dose. One dose-limiting toxicity (DLT) occurred at DL 5 (grade 4 fatigue, pain) and one DLT occurred at DL 6 (G3 headache). However, 5/6 patients required dose reduction on DL6 (G2 nausea, fatigue, hand/foot syndrome, rash). Thus, DL5 (B 10mg/kg, T 20mg, S 200mg twice daily) is being explored in dose expansion (N=10) and tumor expansion cohorts as the recommended phase II dose. The most common adverse events (>10%) were fatigue (69%; G3/4 6%), nausea (38%, G3/4 2%), pain (35%, G3/4 10%), thrombocytopenia (33%, G3/4 8%), mucositis (33%, 0%), constipation (29%, G3/4 0%), hand/foot syndrome (23%, G3/4 0%), rash (19%, G3/4 0%), hypertension (17%, 0%), neuropathy (17%, G3/4 0%), diarrhea (15%, G3/4 6%), vomiting (15%, G3/4 2%), headache (12%, G3/4 2%), and hypertriglyceridemia (10%, G3/4 2%). Of 34 patients evaluable for response, 4 had PR including ovarian (-57%, +6m), gastric (-46%, +5m), colorectal (-32%, +5 m), and thyroid (-31%, +6m) cancer. Eight patients had SD for greater than 4 months including ovarian (0%, +7m), colorectal (-5%, +8m), endometrial (-26%, +5m; -16%, +4m; -15%, +6m), leiomyosarcoma (-5%, +6m), squamous lung cancer (-6%, +6m), and triple negative breast (-15%, +4m) cancer. Conclusions: The combination of S, B, and T is well tolerated and demonstrates preliminary evidence of tumor activity in a variety of solid tumors. PK studies at the recommended phase II dose are ongoing. Clinical trial information: NCT01187199.