Interpretive reporting is an established part of the function of many clinical laboratories. Of the three types of information included in these reports, expert system technology is being demonstrated as useful in producing interpretive comments. The ability of expert systems to explain their reasoning and to be easily updated make them superior to prior attempts to computerize this type of interpretation using traditional computer languages. In the future, the broader application of these systems in realistic clinical environments should be expected given recent commercial success in embedding such programs in laboratory instruments.