Cholinesterase inhibitors are the first agents to be successfully developed specifically for the treatment of cognitive decline associated with Alzheimer's disease. Basic knowledge of their pharmacokinetics is important to their appropriate administration. Their pharmacokinetics help determine the magnitude and duration of their pharmacologic effects, and also the manner in which they affect the degree of cholinesterase inhibition and recovery. The clinical utility of measuring these values in daily practice awaits further research. Drug interactions with cholinesterase inhibitors may occur by pharmacokinetic or pharmacodynamic mechanisms. For the most part, interactions that are mediated by the hepatic cytochrome P-450 system have been inadequately evaluated.