During the last decade, a major role has emerged for brain-derived neurotrophic factor (BDNF) in the translation of intrinsic or sensory-driven synaptic activities into the neuronal network plasticity that sculpts neural circuits. BDNF is released from dendrites and axons in response to synaptic activity and modulates many aspects of synaptic function. Although the importance of BDNF in synaptic plasticity has been clearly established, direct evidence for a specific contribution of the activity-dependent dendritic secretion of BDNF has been difficult to obtain. This review summarizes recent advances that have established specific effects of postsynaptic BDNF secretion on synapse efficacy and development. We will also discuss these data in the light of their functional and pathological significance.