A novel actin cDNA has been isolated from an abdominal ganglion cDNA library of Aplysia californica by differential screening. This cDNA of 1596 nucleotides in length encodes a putative actin protein of 41.8 kDa. This protein shows 95.2% identity with another Aplysia actin gene previously shown to be expressed in the muscular sheath of the ganglion (DesGroseillers et al. (1990) Nucleic Acids Res. 18, 3654). However, the 5' and 3' untranslated regions of these cDNAs are completely different. PCR experiments performed with mRNA isolated from dissected neurons, ovotestis or kidney reveal that the gene is expressed in the neurons of the ganglia and in other tissues as well. Southern blot analysis reveals that the neuronal actin gene is a member of a large gene family.