The massively obese patients had an increased risk of cancer and complications from therapy. Chemotherapy in massively obese patients may be complicated by difficulty in calculating body surface area. No guidelines exist for calculating doses by either actual or ideal weight, and the calculated doses may vary by as much as 25%. The pharmacokinetics of antineoplastic drugs in obese patients are poorly understood and are not sufficient to create standards for rational dosing. We propose that patients being treated with curative intent receive full-dose intensity, using body surface area calculated on actual body weight or on ideal body weight with dose escalations if tolerated. Patients who are treated for short-term palliation may be more safely given doses based on ideal body weight.