Numerous questionnaire studies on attitudes towards euthanasia produced conflicting results, precluding any general conclusion. This might be due to the fact that human behavior can be influenced by automatically triggered attitudes, which represent ingrained associations in memory and cannot be assessed by standard questionnaires, but require indirect measures such as reaction times (RT) or electroencephalographic recording (EEG). Event related potentials (ERPs) of the EEG and RT during an affective priming task were assessed to investigate the impact of automatically triggered attitudes and were compared to results of an explicit questionnaire. Explicit attitudes were ambivalent. Reaction time data showed neither positive nor negative associations towards euthanasia. ERP analyses revealed an N400 priming effect with lower mean amplitudes when euthanasia was associated with negative words. The euthanasia-related modulation of the N400 component shows an integration of the euthanasia object in negatively valenced associative neural networks. The integration of all measures suggests a bottom-up process of attitude activation, where automatically triggered negative euthanasia-relevant associations can become more ambiguous with increasing time in order to regulate the bias arising from automatic processes. These data suggest that implicit measures may make an important contribution to the understanding of euthanasia-related attitudes.