Previous results have shown that following bilateral severence of the optic tracts or transplantation of the optic lobes in the cockroachLeucophaea maderae the circadian pacemakers in the optic lobes are able to regenerate those neural connections with the midbrain that are necessary to drive the activity rhythm (Page 1982, 1983 a). In the present experiments the possibility that the entrainment pathway that mutually couples the two optic-lobe pacemakers is also capable of regeneration was investigated. The results showed that (a) following unilateral optic-lobe transplantation or optic-tract section, regeneration of the coupling pathway did not occur, (b) an optic lobe that remained intact was able to completely suppress the expression of a contralateral pacemaker that had been forced to regenerate its output connections, and (c) if the host optic lobe had also been forced to regenerate its connections with the midbrain after unilateral optic-lobe transplantation, there was frequently evidence for two apparently independent periodicities in the activity pattern. The results indicate that the output pathway by which each oscillator controls activity is functionally independent of the output pathway that couples each oscillator to the contralateral optic lobe. The data also suggest that the regulation of activity by each optic-lobe oscillator may involve a pathway by which activity driven by the contralateral pacemaker can be suppressed.