It has long been an unsolved problem of online market research conducted by means of Access panel sample surveys, that there has been no possibility to verify whether a participant in a survey is really the same who was requested to take part in the survey by means of an e-mail message addressed to him. b2b target groups, for example it decision makers or doctors, are conceivable as examples. there has for a long time been no practical way of verifying whether they fill out an online questionnaire themselves, or forward it, for example, to a secretary or a receptionist to answer (perhaps in order to claim the incentive them-selves). however even in case of consumer research, it is important that, for example, drafts of advertisements which are intended for target audiences of women are filled out by the women panelists and not, for example, by their male partners.of course it would be possible to verify, for example, telephonically whether an invitee had also filled out the online questionnaire, but this is very seldom done in practical research. mainly on account of cost considerations, one would have to restrict oneself to random samples. in addition, there would be a media disruption between online polling and telephonic field checks. not everyone is willing to be interviewed online, because he can estimate the personal advantages of this type of polling (e.g. to choose the time of participation by himself, and not to have any contact with the interviewer), and telephonic contact for the purpose of field checking would in direct apposition. telephonic checks would be perceived thereby as a burden and an annoyance, and willingness to participate in panels and interviews would probably decline. Furthermore, in case of participant authentication via telephone, the time and cost advantages of online research would be at least partially reduced. in the process of validation one would also have to take into consideration those polled answered truthfully. the same applies to a theoretically conceivable personal field survey, in case of which a survey conducted in writing or online, the initial problem of ensuring or verifying that the intended target person fills out the online questionnaire himself would not have been solved.