Morbidly obese patients undergoing bariatric surgery commonly have multiple obesity-related comorbidities, including hypertension (HTN), diabetes mellitus (DM), hyperlipidemia (HLP), and gastroesophageal reflux (GERD). Medical management of these conditions can be costly. The aim of this study was to determine changes in the monthly prescription medication costs in morbidly obese patients who underwent laparoscopic gastric bypass. We examined the data on 77 morbidly obese patients receiving medications prescribed for GERD, DM, HTN, and/or HLP before and after laparoscopic gastric bypass. Changes in medication usage were recorded at 3-month intervals. The retail cost for these medications was obtained from drugstore.com. There were 55 women with a mean age of 45 +/- 11 years. The mean body mass index was 47 +/- 6. The mean excess body weight loss was 67 +/- 14 per cent at 1 year. The mean number of prescription medication per patient was reduced from 2.4 preoperatively to 0.2 at 12 months after surgery. The mean monthly medication cost decreased from dollars 196 preoperatively to dollars 54 one month after surgery, representing a 72 per cent cost savings. One month postoperatively, medication cost saving for GERD was 81 per cent; for DM was 69 per cent; for HLP was 53 per cent; and for HTN was 43 per cent. The mean monthly medication cost savings for the first year after surgery was dollars 168, with a yearly savings of dollars 2016 per patient. Improvement of GERD, DM, HLP, and HTN occur as early as 1 month after laparoscopic gastric bypass results in substantial monthly medication cost savings.