We recently identified Neural Wiskott-Aldrich Syndrome Protein (N-WASP) from bovine brain. An expression analysis using bovine cDNA revealed that N-WASP plays critical roles in the regulation of the cortical actin cytoskeleton. Here, we report the molecular cloning of N-WASP homologs from human and rat brain cDNA libraries. The predicted amino acid sequences of human and rat N-WASP show 96% and 95% identity to bovine N-WASP, respectively, suggesting the functional importance of the molecule. Antibody raised against recombinant rat N-WASP recognizes a 65-kDa protein that exists ubiquitously in whole brain, including cerebrum, cerebellum, interbrain, and medulla oblongata. N-WASP was shown to be concentrated at the nerve terminal region. The gene locus of human N-WASP was also determined at 7q31.3 by fluorescence in-situ hybridization (FISH) analysis.