This article presents results of a comparison between paper and computer tests of ability in Chemistry and Computing. A statistical model is employed to analyse the experimental data from almost 200 candidates. It is shown that there is no medium effect when specific traditional paper examinations in Chemistry and Computing are transferred into electronic format. The effect of rewording for computer-delivered test questions is also investigated and again the conclusion is that no evidence of a difference could be found. These results were obtained as part of the Project for Assessments in Scotland using Information Technology (PASS-IT). © British Educational Communications and Technology Agency, 2005.