Interactions between simultaneously recorded pairs of neurons in the magnocellular and gigantocellular fields of the reticular formation were studied in unanesthetized, unrestrained cats. Each cell pair was recorded during both waking and REM sleep. Dependencies in discharge between spike trains were observed visually and with cross-correlation analyses. These dependencies were present at both short-latency and long-latency intervals. Dependencies were observed with equal frequency in waking and REM sleep. Short duration (1 to 3 ms) interactions were found in 40% of significant cross correlations and were most common in adjacent cells with related behavioral correlates. Patterns of discharge in REM sleep were similar to those in waking. These results suggest that there is common synaptic input to a large proportion of adjacent reticular cell pairs during both waking and REM sleep. Synchronized firing in local cell clusters may be a way in which reticular formation contributions to complex motor behavior are synthesized.