Lithium reverses at millimolar concentrations and in a dose-dependent manner the inhibition of meiotic reinitiation (GVBD) induced by an activator of adenylate cyclase, forskolin, and does this independently of exogenous myo-inositol. These results argue for a pivotal role of adenylate cyclase in the regulation of meiotic resumption and for a possible action of lithium on G proteins rather than at the level of phosphatidylinositol resynthesis.