This study assessed the ability of 426 students (ages 12-13) to critically evaluate two types of online locations on health issues: an academic resource and a commercial resource. The results indicated limited evaluation abilities, especially for the commercial resource, and only a small, partial association with prior stance and offline reading ability. Only about half (51.4%) of the students questioned the credibility of the commercial online resource and only about 19% of the students showed an ability to fully recognize commercial bias. Wide variation existed in students' ability to evaluate online information, as approximately one-fourth of the students performed poorly when evaluating the overall credibility of both online resources and one-fourth performed well. Logistic regression models showed that offline reading skills accounted for only 8.8% of the variance for the academic online resource and 15.1% of that for the commercial resource. No association appeared between evaluation and background knowledge, although an association with prior stance was observed for each online resource. The results are discussed in light of previous research and the need to pay greater attention to the critical evaluation of online resources during classroom instruction.