A variety of adjuvant trials performed in the United States for osteogenic sarcoma, breast, lung, and colon cancer have achieved encouraging results and are briefly summarized. Trials in osteogenic sarcoma are reporting 2-year disease-free survival rates of 50%. However, they have only been evaluated against historical controls and there is some evidence that other factors might have greatly improved the disease-free survival in the absence of adjuvant therapy. The NSABP breast cancer trial only shows significant improvement for women under 50 years of age with 1 to 3 positive axillary nodes. A very promising trial using intrapleural BCG immunotherapy for squamous cell lung cancer is described. Also, two trials of 5-fluorouracil for colo-rectal cancer, both showing trends suggesting slight improvement among treated patients, are presented. Proper care in the design of adjuvant trials with sufficient attention paid to prognostic variables is urged.