There is no clear consensus as to which is the best operation in bariatric surgery. Perhaps a better question is, Which is the right operation for the given patient? No operation is uniformly accepted as the best one. There are too many confounding factors to make this kind of decision making possible. Primarily, the lack of long-term follow-up, established definitions of success, and paucity of randomized data make this unfeasible. In addition, patients may have different goals or biases that determine which operation they choose. Importantly, not all bariatric surgeons perform all bariatric procedures. The preceding sections have reported the outcomes of laparoscopic adjustable banding (LAGB), roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG) and the biliopancreatic diversion/duodenal switch (DS) operation. Specific considerations have also been covered for adolescent patients. This chapter attempts to put these data into perspective and offer recommendations that are suitable for a particular patient or clinical circumstance. The appropriate choice of operation begins with a full assessment of the patient's reasons for choosing as well as expectations of weight loss surgery. Information can then be gathered from the history and physical examination, laboratory data, imaging and endoscopic studies, and prior operative notes. Arbitrarily, choice of procedure can be determined by weight, presence of comorbid illness, age, plans of conception, or relevant previous surgery. Collectively, some of these factors can be used to determine a patient's perioperative risk, which might represent an independent way to choose an operation. For example, what would be the best operation for a 26-year-old superobese man with a history of a previous Nissen fundoplication? Certainly even the most singularly aligned surgeon to a particular operation might give pause to the fact that there needs to be particular consideration in this case and that his or her best operation, or any operation for that matter, may not be appropriate. The four most commonly performed procedures for morbid obesity at this time are RYGB, LAGB, DS, and SG. Each procedure has advantages and disadvantages; accordingly, it is important to consider multiple factors when recommending the type of surgery. Few randomized trials exist comparing the different procedures. Algorithms using review of the literature have been developed to match a given patient to a given operation. This algorithm has not yet been tested in a clinical setting and cannot be absolute.