The Cognitive Drug Research (CDR) computerized assessment system has been in use in worldwide clinical trials for over 20 years. It is a computer based system which assesses core aspects of human cognitive function including attention, information, working memory and long-term memory. It has been extensively validated and can be performed by a wide range of clinical populations including patients with various types of dementia. It is currently in worldwide use in clinical trials to evaluate new medicines, as well as a variety of programs involving the effects of age, stressors illnesses and trauma upon human cognitive function. Besides being highly sensitive to drugs which will impair or improve function, its utility has been maintained over the last two decades by constantly increasing the number of platforms upon which it can operate. Besides notebook versions, the system can be used on a wrist worn device, PDA, via tht telephone and over the internet. It is the most widely used automated cognitive function assessment system in worldwide clinical research. It has dozens of parallel forms and requires little training to use or administer. The basic development of the system wil be identified, and the huge databases (normative, patient population, drug effects) which have been built up from hundreds of clinical trials will be described. The system is available for use in virtually any environment or type of trial.