The hippocampus is a brain structure of pivotal role in many physiological and pathological responses including memory formation, epilepsy and ischemia. Understanding of these processes requires a good knowledge of hippocampal neurons. In vitro culture offers a tool to study these cells in a controlled environment. In order to optimize culture conditions several growth parameters were investigated in hippocampal neuronal cultures derived from rats of different age: 18-day old fetuses, newborns and 5-day old rat pups, maintained in either serum-containing or chemically defined media. Usefulness of particular culture conditions for special purposes is discussed.