Vitamin B is often recommended in the popular media as a systemic repellent against mosquitoes. This information is especially prevalent on the Web. The results of a small number of published studies suggested that vitamin B complex supplements are not effective as repellents, but these studies were limited by the use of very few human subjects and only 1 species of mosquito, Aedes aegypti. We extended this work with the use of larger samples of human subjects and with Anopheles stephensi as the test organism. We tested whether ingestion of vitamin B supplements under various regimens affected the attractiveness of volatile skin components transferred to glass vials. Although there was substantial and consistent individual variation in attractiveness, we found no effect of vitamin B supplementation.