We have reexamined the possibility that cumulus cell cAMP can enter the oocyte via the gap junctions connecting the two cell types (Schultz et al., 1983a). Since our recent results indicate that the mouse oocyte possesses a very active cyclic nucleotide phosphodiesterase (PDE) (Bornslaeger et al., 1984), we have altered our experimental protocol to ensure that mouse oocyte PDE activity is inhibited throughout the duration of an experiment. Our results demonstrate the apparent transfer of cAMP from cumulus cells to the oocyte; these results are discussed in terms of current models for regulation of mammalian oocyte maturation.