The perception of simulation program interfaces by Electrical and Electronic Engineering undergraduate students has been evaluated. Two CAL programs which utilize different interface techniques were used. One program has a tree-structured menu approach to dialogue. The other employs direct manipulation of icons together with context-sensitive menus and dialogue boxes. Data was collected from a conventional amplitude modulation experiment in pre- and post-tests, and from a questionnaire and observations of laboratory sessions. A discussion of the experimental procedures together with a discussion of the results forms the main subject of the paper. The evaluation showed an increase in post-test scores significant at better than 1% for both programs. There was no significant test score difference between the two programs. However, the direct-manipulation program rated more favourably for 21 out of 22 questionnaire statements.