The chapters in the previous section focused on questions that could be addressed with intact-animal models of the epilepsies. In Section 2, there is an attempt to deal more directly with mechanisms that may underlie epileptiform properties that give rise to, for example, the models discussed in Section 1. Two broad issues are addressed by the chapters in this section, (a) What are the features of epileptic brain, i.e. what are the mechanisms that might underlie the production of abnormal epileptiform activities? (b) What do we know about the processes of epileptogenesis itself, i.e., how does the epileptic brain become epileptic? Most of our understanding of underlying mechanisms is derived from studies on brain (or brain tissue) that is already epileptic; we have a still minimal insight into the process of epileptogenesis. Studies have begun to establish which brain attributes are correlated with epileptiform (i.e., abnormal) activities and are providing clues about the consequences of seizure activity; however, initial ‘cause’ is, in most cases (and models) still to be determined. It has been tricky to separate the underlying features of epileptogenesis from characteristics of the already epileptic tissue.