Differences in electrophysiological properties between pyramidal and nonpyramidal neurons have been previously demonstrated in the hippocampal slice preparation. However, it has also been shown that nonpyramidal neurons from several hippocampal regions have different morphologies as well as different active membrane characteristics. In this study, active and passive electrophysiological characteristics of pyramidal and a single morphological type of nonpyramidal neuron in rat dissociated hippocampal culture were examined with intracellular recording at room temperature and at 33-35 degrees C. No significant differences were noted between the two groups of neurons, at either temperature, with regard to action potential amplitude, rate of rise and fall, duration at half maximal amplitude, adaptation to steady state depolarization or resting membrane potential and input resistance. We conclude that these electrophysiological properties cannot be used to distinguish these two neuron types in dissociated hippocampal cell culture.