Scientists have observed theta rhythms (3-12 Hz) in the hippocampus for decades, but we still do not have a clear understanding of how they are generated. This is largely due to the complex, multi-scale and nonlinear nature of our brains. We have developed cellular-based network models of the hippocampus based on a whole hippocampus preparation that spontaneously generates theta rhythms. Building on theoretical analyses and performing thousands of simulations, we find that spike frequency adaptation and post-inhibitory rebound constitute a basis for theta generation in large, minimally connected CA1 pyramidal network models. The contribution of post-inhibitory rebound is necessary given cellular adaptation mechanisms but the theta frequency is not directly controlled by it. Our models can serve as a platform on which to develop an understanding of in vivo theta, and of microcircuit dynamics in the hippocampus. Speaker(s): Frances Skinner (Krembil Research Institute, Toronto University Health Network)