Neurotrophins use two types of receptors, the Trk tyrosine kinase receptors and the p75 neurotrophin receptor (p75NTR), to regulate the growth, development, survival and repair of the nervous system. These receptors can either collaborate with or inhibit each other's actions to mediate neurotrophin effects. The development and survival of neurons is thus based upon the functional interplay of the signals generated by Trk and p75NTR. In the past two years, the signaling pathways used by these receptors, including Akt and MAPK-induced signaling via Trk, and JNK, p53, and NF-kappaB signaling via p75NTR, have been identified. In addition, a number of novel p75NTR-interacting proteins have been identified that transmit growth, survival, and apoptotic signals.