Soluble N-ethylmaleimide-sensitive factor attached protein receptor (SNARE) molecules are implicated in many fundamental cellular processes that require membrane fusion, and the interactions of the SNARE proteins, SNAP-25, syntaxin and VAMP/synaptobrevin, have been extensively studied. This review documents recent data on their role at different stages of development. SNARE proteins are expressed very early and play important roles in fertilization and in cell division during early embryogenesis. In the developing nervous system, they are important for neurite outgrowth and transformation of the growth cone into the mature synapse. In the neuroendocrine system, in addition to neurosecretion, they are involved in processes related to morphological plasticity. Although few data exist on regulation of SNARE proteins during development, growth factors, intracellular messengers and depolarization are known to modify their cellular expression. The putative importance of these factors during development is discussed.