Copyright © 2015 Massachusetts Medical Society. BACKGROUND BRAF V600 mutations occur in various nonmelanoma cancers. We undertook a histology-independent phase 2 "basket" study of vemurafenib in BRAF V600 mutation- positive nonmelanoma cancers. METHODS We enrolled patients in six prespecified cancer cohorts; patients with all other tumor types were enrolled in a seventh cohort. A total of 122 patients with BRAF V600 mutation-positive cancer were treated, including 27 patients with colorectal cancer who received vemurafenib and cetuximab. The primary end point was the response rate; secondary end points included progression-free and overall survival. RESULTS In the cohort with non-small-cell lung cancer, the response rate was 42% (95% confidence interval [CI], 20 to 67) and median progression-free survival was 7.3 months (95% CI, 3.5 to 10.8). In the cohort with Erdheim-Chester disease or Langerhans'-cell histiocytosis, the response rate was 43% (95% CI, 18 to 71); the median treatment duration was 5.9 months (range, 0.6 to 18.6), and no patients had disease progression during therapy. There were anecdotal responses among patients with pleomorphic xanthoastrocytoma, anaplastic thyroid cancer, cholangiocarcinoma, salivary-duct cancer, ovarian cancer, and clear-cell sarcoma and among patients with colorectal cancer who received vemurafenib and cetuximab. Safety was similar to that in prior studies of vemurafenib for melanoma. CONCLUSIONS BRAF V600 appears to be a targetable oncogene in some, but not all, nonmelanoma cancers. Preliminary vemurafenib activity was observed in non-small-cell lung cancer and in Erdheim-Chester disease and Langerhans'-cell histiocytosis. The histologic context is an important determinant of response in BRAF V600-mutated cancers.