Designers and developers of courseware are inclined to use audio (and speech in particular). But they are facing educational problems: hardly anything is known about the use of audio in instruction with respect to the processing of visual and auditive information, learner characteristics, events of instruction, and audio characteristics. In this article information on each of these items is given. Where possible, literature is reviewed. The conclusion of this article is that some research has already been done in this area but in order to obtain more design knowledge on the use of audio in courseware, much more (multi‐disciplinary) research is required. Only a minimum of factors related to the use of audio in courseware is mentioned here. Designers should be aware of that. Some other aspects of audio, which are not mentioned here, are the number of voices, gender of speaker and of listener, and listening comprehension. We present research results about aspects of audio, used in courseware, that are available. The design principles that can be extracted from the research reviewed will be summarized in the concluding section.