The ventrolateral region in the medulla of cats was explored with pairs of microelectrodes with tip separations from 100 to 300 micron such that extracellular potentials of pairs of near-neighboring neurons were recorded simultaneously. At least one neuron of each pair was antidromically activated from the spinal cord. Cross-correlation histograms were computed and showed the existence of short-term synchronization of firing for 8 of 20 neuron pairs (40%). The primary feature of the cross-correlation histograms was, typically, asymmetrical peaks on each side of time zero. The peaks were dissimilar, one low and broad, the other high and narrow, and occurred within a millisecond of time zero. Poststimulus histograms computed for one of the pair, during antidromic activation of the other, indicated a possible interaction between the neurons in one case but not in another. The results are suggestive of neuronal interactions among the late-firing inspiratory neurons of the nucleus retroambigualis but are not conclusive.