Pacsins are cytoplasmic adapter proteins with an N-terminal FHC, a central coiled coil, and a C-terminal SH3 domain and several potential phosphorylation sites. Two murine Pacsin genes have been reported to date: Pacsin 1 (equivalent to rat Syndapin I), and Pacsin 2 (like rat Syndapin II and chicken focal adhesion protein FAP52). Rat syndapins have been well characterized as part of a synapse dynamin-associated protein complex involved in endocytosis and actin dynamics. Here we describe PACSIN 3, a third member of the pacsin gene family in humans and mice, which encodes a 424 amino acid cytoplasmic protein and has a ubiquitously expressed mRNA. Intracellular distribution was assessed by overexpression of exogenous tagged pacsin 3 protein. In addition, we report the cDNA sequence of human PACSIN 1, a gene encoding a 444 amino acid protein and its chromosome assignment to 6p21. PACSIN 1 mRNA is most abundant in brain, and is also present in heart, pancreas and liver. The close sequence conservation between the three pacsin gene products suggests they could be performing similar functions participating in the different tissues where these are expressed.