AbstractResearchers considering novel or exploratory psycholegal research are often able to easily generate a sizable list of independent variables (IVs) that might influence a measure of interest. Where the research question is novel and the literature is not developed, however, choosing from among a long list of potential variables those worthy of empirical investigation often presents a formidable task. Many researchers may feel compelled by legal psychology's heavy reliance on full‐factorial designs to narrow the IVs under investigation to two or three in order to avoid an expensive and unwieldy design involving numerous high‐order interactions. This article suggests that fractional factorial designs provide a reasonable alternative to full‐factorial designs in such circumstances because they allow the psycholegal researcher to examine the main effects of a large number of factors while disregarding high‐order interactions. An introduction to the logic of fractional factorial designs is provided and several examples from the social sciences are presented. Copyright © 2002 John Wiley & Sons, Ltd.