In 1994, it was proposed that decision-making requires emotion-related signals, known as somatic markers. In contrast, some authors argued that conscious knowledge of contingencies is sufficient for advantageous decision-making. We aimed to investigate the respective roles of somatic markers and explicit knowledge in decision-making. Thirty healthy volunteers performed the Iowa Gambling Task (IGT). Conscious knowledge was assessed using a sensitive questionnaire and skin conductance responses (SCRs) were recorded. Most participants acquired a preference for advantageous choices during the task and generated larger anticipatory SCRs before disadvantageous relative to advantageous choices. Performance on the IGT and the autonomic response were positively correlated (r = 0.38, p = 0.045). Moreover, there was a statistically significant difference in performance according to conscious awareness (p = 0.009). There was no significant association between level of explicit knowledge and SCR (p = 0.1). Finally, we did not find any interaction between explicit knowledge and performance although a lack of statistical power is not to be excluded. Advantageous decision-making therefore seems to be associated with two distinct, namely implicit and explicit, systems. (Contains 2 figures.)