This study sought to determine the effects of prior knowledge on the achievement of undergraduates in an economics course at the Open University of the Netherlands (OuN). A total of 49 law and 39 economics students were given 4 instruments to test prior knowledge of economics, presented with a learning unit from the course "Economics and Money," and then post-tested on subject mastery. Multiple regression analysis of the results demonstrated that prior expertise accounted for 16 to 17 percent of the variance in posttest scores. The results indicated that study time was not a relevant independent variable and did not help explain variance in posttest scores. (Contains 16 references.) (MDM)