The purpose of this study was to assess the effectiveness of two different methods of online education using the knowledge base of African horse sickness (AHS) among US equine veterinarians as a model. An e-mail was sent to US veterinary members of the American Association of Equine Practitioners (AAEP), inviting them to participate in a complementary online educational opportunity. We determined participants' baseline knowledge of AHS by their responses in an AHS case scenario. Participants were then randomly assigned to either a Webinar module or a text-formatted module, followed by an educational assessment quiz. Educational effectiveness was measured by considering the difference between the educational assessment quiz score and the baseline knowledge score. Of the 5,394 members from the AAEP list, 309 veterinarians agreed to participate, but only 211 completed the entire study. The median baseline knowledge score from the case scenario was 20 out of a perfect score of 100 points. The median assessment quiz score after the participants had access to the AHS educational material was 90, which was significantly higher than the baseline knowledge score (p=.01). Educational effectiveness in the module formats showed no significant difference (p=.81). Results from this study suggest that online education modules, once accessed, may improve participants' knowledge of veterinary diseases.