Non-adherence is a public health problem costing over $100 billion/year. Patients lack of belief in the medication benefits and lack of information about the drug are important determinants of medication adherence. The Internet may be a pathway to improving patient knowledge. Although 73 million Americans have used the Internet to seek health information, little is known about the consequences of this eHealth behavior. Adapted scales assessing eHealth self-efficacy, perceived impact of using eHealth, and Personal eHealth Information Outcomes Expectations were tested within the theoretical framework of the Social Cognitive Theory. EHealth self-efficacy is defined as an individuals perception of his or her ability to use the Internet to find health resources. In a cross-sectional design, 132 adults completed a 43-item online survey. Higher levels of eHealth Self-efficacy are significantly associated with eHealth use (r=0.21, p<0.05), Web browsing self-efficacy (r = 0.34, p<0.01), Personal eHealth Information Outcomes Expectations (r = 0.34, p<0.01), Computer Anxiety (r=-0.24, p<0.01) and Perceived Impact of using the eHealth information (r = 0.32, p<0.01). A randomized controlled trial evaluated the impact of eHealth information seeking on patients medication adherence, knowledge, attitudes, and patient-provider relationships. The intervention consisted of eHealth Web sites linked in a Web portal. Eighty-one Internet users taking medications for diabetes, dyslipidemia, and/or hypertension participated in the 2-month prospective study. No significant differences on the outcomes measures were noted between experimental groups. However, clinically significant changes in medication dosage, contacts with doctors, and increased awareness of potential side effects were observed among the eHealth information participants. The third study identified opinions, preferences and types of behaviors regarding eHealth information use, for health professionals and patients in United States and Europe. In a cross-sectional design (n=2621 respondents, USA 38%; Europe 29%), health professionals preferred using medical search tools but patients preferred general search tools. 69% USA patients and 47% European patients have discussed their eHealth findings with their doctors. Instruments with evidence of reliability and validity to assess constructs like eHealth self-efficacy should be useful to eHealth behavioral research. More research is needed to evaluate the impact of eHealth use on medication adherence and knowledge.