Cell-cell signaling within the neocortical ventricular zone (VZ) has been shown to influence the proliferation of VZ precursor cells and the subsequent differentiation and fate of postmitotic neurons. Calcium (Ca(2+)), a ubiquitous second messenger implicated in the regulation of many aspects of development, may play a role in these signaling events. Accordingly, we have examined the spatiotemporal patterns of spontaneous intracellular free Ca(2+) (Ca(2+)) fluctuations of cells within the intact neocortical VZ. Previous observations have demonstrated that similar patterns of spontaneous Ca(2+) increase occur in both proliferative and postmitotic cortical cells, suggesting that they may be mechanistically similar. Our results suggest that the changes in Ca(2+) in VZ cells and cortical plate neurons are likely triggered by different mechansims, and imply that similar changes in Ca(2+) may underlie different signaling events during distinct phases of neocortical development.