Personal digital assistant sales are growing exponentially, and as medical technology advances the amount of information available becomes staggering, making a handheld device, with the ability to store a great amount of information, progressively more valuable to health care providers. Mobile computing allows for a great deal of knowledge in a small package, creating a "walking library" with a mobile collection of data always accessible. There are many diverse types of PDAs, and this article discusses the history of PDAs, general purchasing issues, general PDA features, and the most significant differences between the Palm and the Windows CE operating systems.