To address the recognized problems associated with information overload and limited human memory, computer-based systems which help healthcare providers use information to make better decisions have been developed and implemented. These decision aids are designed to improve the quality and reduce the cost of healthcare. Currently, the most widely used computer application is to simply provide needed facts about the patient in an organized and timely fashion. Additionally, healthcare workers can access literature, ask questions of aggregates of patient data for clinical or administrative decisions, receive warnings or suggestions when the patient's data satisfy certain logical rules receive critiques when proposing therapies or ordering diagnostic tests, receive guidelines for standards of care, access programs which analyze tradeoffs and likelihoods of alternative outcomes (decision analysis) and receive lists of differential diagnoses. Given this wonderful panoply of capabilities, the question becomes 'why aren't more people using these aids and what are the demonstrated benefits of such capabilities?' In this paper we review the types of decision aids which have been successfully implemented and the challenges to implementation (knowledge representation, connections to databases, need for comprehensive, coded databases and evaluation of benefits).