The American College of Surgeons Oncology Group (ACOSOG) conducts cancer trials that are relevant to surgeons who treat patients with breast, thoracic, and gastrointestinal cancers. ACOSOG is funded by the National Cancer Institute and is charged with conducting prospective clinical trials that address important questions in academic and community practice settings. Examples include role of axillary dissection for microscopic nodal disease, neoadjuvant therapy for organ-conserving surgery, laparoscopic rectal cancer resection, mediastinal nodal staging, and sublobar resection for early-stage non-small cell lung cancer. Such trials are relevant to most practicing surgeons.