We would like to caution readers against drawing inappropriate cause-and-effect conclusions from the results presented in this paper. A goal of this paper is to present data based on existing empirical literature. As demonstrated by our finding of only one study in which random assignment of individuals to conditions occurred, there is a tremendous need for experimental studies of Web-based instruction if we are to draw any definitive conclusions about the effectiveness of Web-based instruction in comparison to other methods. The conclusions that one can draw from the results of a meta-analysis are highly dependent on the research designs of the individual studies examined. For example, if all the studies included are correlational, as were many of the studies reviewed in this paper, associational rather than causal conclusions are more appropriate. In this paper, the terms “effect,” “effect sizes,” and “effectiveness” are used in accordance with the accepted technical language of meta-analysis and are not meant to necessarily imply the existence of causal relationships.