OBJECTIVES: The objective of this study was to identify the national rates of co-prescribing cholinesterase inhibitors with anticholinergic urinary incontinence medications using the National Ambulatory Medical Care Survey (NAMCS) and the National Hospital Ambulatory Medical Care Survey (NHAMCS). Anticholinergic classes of medications have a mechanism of action that opposes the cholinesterase inhibitors; therefore, when taken concomitantly the effectiveness of these medications potentially decreases. The objective of this study was to describe the concomitant prescribing of cholinesterase inhibitors and anticholinergic drugs indicated for urinary incontinence.  METHODS: This study was a retrospective, observational, cross-sectional, database analysis using data from the 2006-2008 NAMCS and NHAMCS outpatient departments. Patient visits that included a prescription for a cholinesterase inhibitor alone or combined with an anticholinergic medication approved for urinary incontinence were analyzed. The data was weighted to produce national estimates and analyzed using descriptive statistics.  RESULTS: Over the 3 year period there were 13,345,926 visits including cholinesterase inhibitors. Of the visits including a cholinesterase inhibitor, 5.5% (n=737,064) also included a prescription of an anticholinergic urinary incontinence medication. The most commonly prescribed cholinesterase inhibitor was donepezil (n=11,173,472; 83.5%). The majority of patient visits that included the prescription of both a cholinesterase inhibitor and an anticholinergic medication were made by patients over 80 years of age (n=404,359; 54.9%). The most common physician specialty to prescribe both cholinesterase inhibitors alone (n=6,587,573; 49.2%) and the combination with an anticholinergic medication (n=333,135; 45.2%) were family practitioners and general practice/internal medicine. Urologists and obstetricians/gynecologists represented the prescribing physicians in 16.8% (n=123,465) of visits with combination therapy, whereas they accounted for 3.1% (n=415,818) of the cholinesterase inhibitor prescribing.  CONCLUSIONS: Cholinesterase inhibitors and anticholinergic urinary incontinence medications were inappropriately prescribed together. Educating health care providers and patients about this potential interaction can optimize drug therapy for patients on cholinesterase inhibitors.