The development of new computer-administered neuropsychological tests has brought a renewed focus on the issue of written instructions. Designers and programmers often fail to take advantage of the display options and feedback potential available in modern computer systems to maximize the effectiveness of the instruction process. Guidelines from computer interface architecture and behavioral analysis are combined to present three principles for written instructions: precise language, attention focusing, and interactive instruction. A comparison of different instruction formats in the Symbol-Digit and Simple Reaction Time tests shows that the application of these principles can reduce training time without degrading performance.