Neurofilaments (NF) constitute the predominant intermediate filament components of the neuronal cytoskeleton. While the structural properties of NF are well understood, less is known about their function. Protein phosphorylation appears to play a key role in regulating aspects of NF behavior, such as subunit polymerization and axonal transport. Local regulation of NF phosphorylation may govern variations in the size and morphology of the NF matrix in different regions of the neuron. However, few kinases responsible for these modifications have been identified. This dissertation aimed to identify and characterize proteins which interact with NF, with particular emphasis on protein kinases. Several approaches were used. Firstly, a panel of monoclonal antibodies (MAbs) specific for NF-associated proteins was characterized. MAbs were analyzed by coimmunoprecipitation and immunocytochemical assays. The ligand of one MAb, which coprecipitated with NF, was found to be synapsin I. This synaptic vesicle-associated protein modulates synaptic vesicle function by association with the cytoskeleton. The association of synapsin I with NF may also contribute to this function. The second approach used coimmunoprecipitation assays to assess whether various neuronal kinases interact with NF in brain tissue. An association between a novel cdc2-related kinase and NF was detected. In vitro kinase assays demonstrated that immunoprecipitated cdc2-related kinase phosphorylates NF. The expression of a cdc2-like protein in mature brain tissue suggests that the role of this protein differs from that of other cdc2-related proteins. Previous studies have suggested that NF phosphorylation is regulated by myelination of neurons. This study tested the effect of myelination on NF phosphorylation by examining co-cultures of dorsal root ganglion neurons and Schwann cells. NF were shown to be more highly phosphorylated in myelinated cultures compared to unmyelinated, thus demonstrating that myelination alone is sufficient to induce changes in NF phosphorylation. The activities of individual NF kinases were compared in myelinated and unmyelinated cultures, and candidate kinases which may phosphorylate NF in response to myelination were identified. Collectively, this study has demonstrated the feasibility of these approaches for the identification of proteins that bind or modify NF. What remains to be discovered is how these proteins affect NF function and dynamics in neurons.