Individuals with questions about their health often turn to the Internet for information about their symptoms, but the degree to which health anxiety is related to online checking, and clinical variables, remains unclear. The clinical profiles of highly anxious Internet checkers, and the relationship to checking behavior itself, have not previously been reported.In this article, we test the hypothesis, derived from cognitive-behavioral models, that individuals with higher levels of illness anxiety would recall having experienced worsening anxiety after reassurance-seeking on the Internet.Data from 731 volunteers who endorsed engaging in online symptom-searching were collected using an online questionnaire. Severity of health anxiety was assessed with the Whiteley Index, functional impairment with the Sheehan Disability Scale, and distress recall during and after searching with a modified version of the Clinician׳s Global Impairment scale. Multiple regression analyses were conducted to determine variables contributing to distress during and after Internet checking.Severity of illness anxiety on the Whiteley Index was the strongest predictor of increase in anxiety associated with, and consequent to, online symptom-searching. Individuals with high illness anxiety recalled feeling worse after online symptom-checking, whereas those with low illness anxiety recalled relief. Longer-duration online health-related use was associated with increased functional impairment, less education, and increased anxiety during and after checking.Because individuals with moderate-high levels of illness anxiety recall experiencing more anxiety during and after searching, such searching may be detrimental to their health. If replicated in controlled experimental settings, this would suggest that individuals with illness anxiety should be advised to avoid using the Internet for illness-related information.