Gap junction communication plays an essential role in follicle growth. Immunocytochemistry and confocal microscopy were used to examine the expression of gap junction connexins of the alpha and beta subfamilies in follicles from primordial to preovulatory stages in the ovaries of prepubertal and adult mice. Connexin-specific antibodies detected alpha(1), alpha(4), alpha(6), beta(1), beta(2) and beta(4) connexins within follicles. In adult ovaries connexin immunolabelling was stronger in larger (more mature) follicles than it was in smaller follicles, with comparatively reduced labelling detected in prepubertal ovaries. In healthy follicles, labelling for alpha subfamily connexins was detected between granulosa cells, whereas labelling for beta subfamily connexins was found in the theca. Labelling for beta subfamily connexins and alpha(4) connexin (preantral stage) was detected on the oocyte surface membrane. In atretic follicles, labelling for beta(4) connexin appeared between the granulosa cells. These results demonstrate that alpha and beta connexin subfamilies are segregated to separate cellular compartments in the mouse follicle. The results are discussed in the light of possible roles for differential gap junctional communication in the regulation of folliculogenesis, oocyte maturation and atresia.