With steadily rising use of the Internet as a source of health information, public health authorities have expressed concern about the increasing visibility of unscientific information promulgated on the Internet by opponents of childhood vaccination. Searches were made on the four most popular Internet search engines using different combinations of the terms, "vaccination," "immunization," "immunisation," "immunize," "immunise," "vaccine," and "shots." Thirty results were tabulated for each search engine. Searching with the keyword "vaccination" resulted in a significantly higher percentage of antivaccination websites as compared with searches with all other keywords. Of all child-related websites retrieved, the single keyword "vaccination" yielded 40% provaccination sites and 60% antivaccination sites. By contrast, the single keyword "immunization" yielded 98% provaccination sites and 2% antivaccination sites. Using a combination of the words "vaccination" and "immunization" produced results between these two extremes. Thus, any use of the term "vaccination" during an Internet search is likely to expose a parent to a significant amount of antivaccination information. Recommendations are discussed for future research and methods to reduce the impact of misinformation on health consumers using the Internet.