This chapter describes the process of synapse development, focusing on the signaling and molecular cues involved in the formation of mammalian central excitatory synapses. It provides an overview of central nervous system (CNS) synapse structure and describes the initial contact between axon and dendrite. Contact between axon and dendrite occurs both en passent along the shaft of the axon and at its growing tip, just as synapses form both on dendritic protrusions and the dendritic shaft. The chapter discusses the differentiation of those pre- and post-synaptic compartments, and the large number of molecules implicated in the regulation of synaptogenesis. It addresses how activity might be involved in the formation and/or maturation of synaptic contacts, and how control of this intricate process might differ in young animals compared to adults or following neural injury. Glutamate release from presynaptic terminals may control axonal filopodia motility and selection of postsynaptic targets.