Postoperative delirium (POD) and Postoperative cognitive dysfunction (POCD) are common significant postoperative complications in elderly patients. A reduction of postoperative complications would lead to improved functional status, greater independence and reduction in health care cost. Scientific evidence shows that acetylcholinesterase inhibitors may reduce incidence and/or severity of postoperative delirium. We propose to conduct a randomized, double-masked, placebo-controlled study to assess effectiveness of Rivastigmine, an acetylcholinesterase inhibitor. Rivastigmine transdermal system (Exelon Patch) is approved by FDA for the treatment of mild to moderate Alzheimer's dementia and mild to moderate dementia associated with Parkinson's disease. Patients 65 y.o. and older undergoing major elective surgery will qualify for the study based on risk assessment guidelines. Patients screening will include Mini Mental Status Examination (MMSE to assess baseline cognitive function), Hamilton scale (to screen for depression), Telephone Interview of Cognitive Status Modified (TICS-M to assess baseline cognitive function over the phone) and Brief Test of Adult Cognition by Telephone (BTACT to assess baseline cognitive function over the phone). All study subjects will be randomly assigned to one of 2 groups prior to surgery. The treatment group will receive a Rivastigmine patch preoperatively covered by tegaderm dressing and a placebo group will receive just a tegaderm dressing. Both groups will be assessed twice daily at 9am and 4pm for up to 72 hours postoperatively with Confusion Assessment Method for Intensive Care Unit (CAM-ICU), Memorial Delirium Assessment Scale (MDAS) and Mini Mental Status Examination (to diagnose delirium and assess its severity). At one month and three months postoperatively subjects with a postoperative MMSE of 27 or less will be assessed for postoperative cognitive dysfunction. The assessment will be performed over the phone with TICS-M and Brief Test of Adult Cognition by Telephone. Outcomes will be divided into Primary and Secondary outcomes. Primary outcome will determine the proportions of patients with at least one episode of POD in the treatment and placebo groups, diagnosed by CAM-ICU. Secondary outcome will determine the proportions of patients with development of POCD in both groups, diagnosed by TICS-M at 1 month postoperatively. Secondary outcome will also determine cumulative number of POD episodes within first 3 days of hospital stay as diagnosed by CAM-ICU, severity of POD as diagnosed by the MDAS, recovery of cognitive function as diagnosed by MMSE, TICS-M and BTACT, and length of hospital stay.