All antiepileptic drugs may provoke positive or negative psychiatric reactions in individual patients. These psy-chotropic effects are not simply idiosyncratic but depend on the drug's anticonvulsive strength and the person's genetic and biographic psychiatric predisposition. Mechanisms related to psychiatric adverse events are polytherapy and folate deficiency, forced normalization, drug toxicity, and withdrawal. Our knowledge on dose independent, idiosyncratic psycho-tropic side effects is still limited. With respect to the older antiepileptic drugs there are almost no systematic data, and knowledge is largely empirical and based on anecdotal reports. With respect to the new generation of anticonvulsants there are data on psychiatric side effects from drug trials. However, these data are not always entirely transparent to the interested epileptologist. Moreover, drug trials are designed to test anticonvulsive efficacy and psychiatric adverse events are not systematically reported, thus severity psychopathologic nature of behavioral problems remain obscure. Differences in patients included in trials do not allow comparisons of psychiatric risks of specific drugs, particularly since following the vigabatrin experience, patients with a psychiatric history were often excluded from trials. In this chapter, methodological issues related to data on psychiatric adverse events of AED are discussed followed by an overview on the current knowledge on psychiatric side effect profiles of old and new antiepileptic drugs.