A sample of 490 high school students from 81 schools in Michigan participated in an experiment in which they were randomly assigned to either a control or an experimental Web site. The experimental Web site provided exposure to educational material about the process of organ donation and organ transplantation. The control Web site provided educational material on methods to avoid the common cold. The pre- and post-tests of knowledge of issues related to organ donation and of attitude toward donation demonstrated statistically significant increases for the experimental group compared with the control group. A structural equation path model suggested that these increases in knowledge and pro-donation attitude mediated the effects of the experiment on contacting the Michigan donor registry. The increase in knowledge and in prodonation attitude increased the likelihood of contacting the registry. The potential for this and similar other Web interventions to enhance students' health education is discussed. (Contains 1 table and 3 figures.)