ABSTRACTPurposeWeb‐based intensive monitoring is a method to actively collect information about adverse drug reactions (ADRs) using patients as a source of information. To date, little is known about patients’ motivation to participate in this kind of active post‐marketing surveillance (PMS). Increased insight in this matter can help us to better understand and interpret patient reported information, and it can be used for developing and improving patient‐based pharmacovigilance tools. The aim of this study is to gain insight into patients’ motives for participating in active PMS and investigate their experiences with such a system.MethodA mixed model approach combining qualitative and quantitative research methods was used. For both parts, patients participating in a web‐based intensive monitoring study about the safety of anti‐diabetic drugs (excluding insulins) were used. A questionnaire was developed based on the results from qualitative interviews. The data collected through the questionnaires was analysed with descriptive statistics. Relations between patient characteristics and motives were analysed using a t‐test or a Chi‐squared test.Results1332 (54.6%) patients responded to the questionnaire. The main motive for participation was altruism. Often experiencing ADRs or negative experiences with drugs were not important motives. The patient's gender played a role in the different motives for participation. For men, potential future personal benefit from the results was more important than for women. The overall opinion about the system was positive.ConclusionThe knowledge that patients participate in this kind of research from an altruistic point of view may strengthen patient involvement in pharmacovigilance. Copyright © 2012 John Wiley & Sons, Ltd.