Cognitive neuroscience research has begun to reveal the functional neuroanatomy of intentional action. This research has primarily pointed to the role of the medial frontal cortex for the voluntary control of behaviour. However, a closer inspection of the literature reveals that the anterior insular cortex (AIC) is also routinely activated in tasks that involve different aspects of intentional action. In the present article, we outline studies that have found AIC activation in various intentional action paradigms. Based on these findings, we discuss two hypotheses about the AIC's contribution to voluntary control. One hypothesis states that AIC is involved in forming intentions, by providing information about the internal states of the system. The alternative view suggests that AIC evaluates the outcomes of intentional action decisions that have been previously formed elsewhere. The limited evidence so far favours the evaluative hypothesis. AIC may provide interoceptive signals that play an essential role in evaluating the consequences of intentional action. AIC is therefore a key structure for the adaptive, affective training of the individual will, on which human society depends.