Neurotrophins are growth factors that modulate growth, differentiation, and survival of neurons. These structurally related proteins include neuron growth factor (NGF/β-NGF), brain derived neurogenic factor (BDNF), neurotrophin-3, and neurotrophin-4/5. They are highly homologous and share a similar structure of a tertiary folded, cysteine rich knot. Neurotrophins are critical to the development of the central and peripheral nervous systems, and they play important roles in injury-induced neuron regeneration. β-NGF is a member of the neurotrophin family which controls growth, survival, and maturation of neurons. In peripheral and central neurons, neurotrophins are important regulators for survival, differentiation, and maintenance of nerve cells. They are detectable throughout embryogenesis and into the adult stage in the central and peripheral nervous systems. In animal models, β-NGF prevents neuronal degeneration and has become a therapeutic target in neuron regeneration studies. β-NGF is also critical for the survival and maintenance of sympathetic and sensory neurons. It is the main neurotrophin that maintains homeostasis of neurogenesis. It prevents neurons from undergoing apoptosis and promotes maturation while supporting axonal branching. Two receptors are known to interact with NGF, p75NTR and TrkA. The NGF-TrkA signaling pathway induces two pathways through activation of PI3K-Akt or Ras-MAPK. Both these pathways leads to CREB phosphorylation and increases expression of anti-apoptosis genes to keep neurons alive. Animal models of neurodegenerative diseases suggest that NGF can promote myelin repair of neurons in the peripheral nervous system. Clinical studies indicate that dysregulation of NGF signaling is related to Alzheimer's disease.