Physicians and parents report a need for pediatricians to have additional training in delivering a diagnosis of Down syndrome (DS). This study tested a web-based tutorial to assess its effectiveness in improving physicians' perceived comfort with both ambiguous and more medically factual situations as they deliver diagnoses of DS. Based on this web tutorial that integrated prenatal and postnatal information into virtual patient scenarios, the study assessed pediatrics residents' knowledge and comfort in delivering a diagnosis of DS pre and postnatally. A separate survey, given at the same time, asked for residents' perception of their need for this training. Ninety-one volunteer residents from 10 pediatric training programs across the country participated. The tutorial yielded significant improvement in knowledge and a significant decrease in perceived level of discomfort in both ambiguous situations and more medically certain contexts related to a DS diagnosis. In addition, across all pediatric resident groups (by year, gender, and performance on the knowledge test and the comfort scale), residents strongly agreed that this type of training was beneficial for themselves, other residents, practicing physicians, and other medical professionals. This study suggests that web-based, interactive, multi-media training may be an effective tool for improving resident physician comfort with both ambiguous and more medically certain situations in delivering a diagnosis of DS to families. © 2012 Wiley Periodicals, Inc.