We conducted an event-related, functional MRI investigation of 12 male's and 12 female's reasoning about conditional deontic rules, rules regulating people's behavior. We employed two different types of rules: social contracts and nonsocial, precautionary rules. Although the rules and the demands of the task were matched in terms of their logical structure, reasoning about social contracts and precautions activated a different constellation of neurological structures. The regions differentially activated by social contracts included dorsomedial PFC (BA 6/8), bilateral ventrolateral PFC (BA 47), the left angular gyrus (BA 39), and left orbitofrontal cortex (BA 10). The regions differentially activated by precautions included bilateral insula, the left lentiform nucleus, posterior cingulate (BA 29/31), anterior cingulate (BA 24) and right postcentral gyrus (BA 3). Collectively, reasoning about prescriptive rules activated the dorsomedial PFC (BA 6/8). The results reinforce the view that human reasoning is not a unified phenomenon, but is content-sensitive.