The multigene family of equinatoxins, pore-forming proteins from sea anemone Actinia equina, has been studied at the protein and gene levels. We report the cDNA sequence of a new, sphingomyelin inhibited equinatoxin, EqtIV. The N-terminal sequences of natural Eqt I and III were also determined, confirming two isoforms of EqtI, differing at position 13. The number of Eqt genes determined by Southern blot hybridization was found to be more than five, indicating that Eqts belong to a multigene family.