The Liverpool Epidemiology Programme, based in the Liverpool School of Tropical Medicine, has designed a series of computer-based modules for use in distance learning. The purpose of this paper is to highlight the role of computers in training health workers in epidemiology in developing countries. The aim of the modules is to provide health workers with solutions to problems which they face in their everyday work. The modules are written in hypertext software for IBM compatible machines and interact with the epidemiological software Epi Info. Four modules are described: LEP-Nut which deals with nutritional surveillance, LEP-Ref which looks at the role of epidemiology within a refugee health care programme, LEP-Surv dealing with health surveillance and LEP-Rap which introduces the concept of rapid appraisal. They are also easily distributed, particularly with the development of the Internet. The modules are carefully evaluated before and after distribution. Issues related to their evaluation and subsequent revision are discussed, in particular is the content important, adequate, communicated and useful? A major advantage of computer-based learning materials is that they can be easily updated with new advancements of knowledge and experience from the field.