Gap junction structures and distribution patterns of immunoreactive connexin46 (Cx46) and connexin50 (Cx50) in normal lenses and lens regrowths of rhesus monkeys were studied using electron microscopy and immunofluorescence double-labeling. Lens regrowths were collected from aphakic eyes of young monkeys whose natural lenses had been surgically removed 11-34 months earlier to simulate monocular congenital cataract surgery in human infants. Approximately 90% of the lens regrowths examined was in the form of a doughnut-shaped Soemmerring's ring located behind the iris. The lens regrowth consisted of lens epithelium and lens fibers enclosed within hypertrophied capsular material. The superficial equatorial region usually contained nucleated young fibers of normal appearance. The other regions consisted of many swollen fibers. Gap junctions were readily observed between fiber cells of both normal and swollen configuration in the lens regrowth. In superficial fibers, gap junctions were not associated with cytoskeletal components. In the intermediate and the deeper cortical regions, actin filament bundles were found specifically associated with gap junctions along both of their cytoplasmic surfaces. An immunofluorescence double-labeling study showed that Cx46 and Cx50 were labeled in the same gap junctions in both superficial and deeper cortical fibers of the normal lens. In contrast, in the lens regrowth strong co-labeling of Cx46 and Cx50 was only observed in the superficial fibers. The labeling for Cx50 was very weak or absent in the deeper cortex, whereas the strong labeling for Cx46 persisted throughout the major portion of the deeper cortex. The labeling for Cx46 finally disappeared in the much deeper cortex. This study shows that (1) the same distribution pattern of actin bundle/gap junction association found in normal lenses is seen in the lens regrowth, and (2) the immunoreactive distribution of Cx46 and Cx50 differ in the lens regrowths as compared with those in the normal lenses of rhesus monkeys.