Gelsolin superfamily proteins control actin organization by severing filaments, capping filament ends and nucleating actin assembly. Gelsolin, a protein of 82–84 kDa, is the founding member of this family, which now contains at least another six members: villin, adseverin, capG, advillin, supervillin and flightless I. Gelsolin exists as a cytoplasmic as well as a plasma isoform, and can bind, sever and cap actin filaments. Plasma gelsolin level decreases dramatically as a result of major trauma and reinfusion of gelsolin can protect against lung damage associated with major burn injury and other types of insults. Recent study in Fas antibody-induced liver failure suggests that gelsolin exerts an overall antiapoptotic effect in vivo. Gelsolin, a marker of motility, could be applied as a biomarker in assessing tumor prognosis. Tumor-associated processes such as invasion and metastasis are known to be critically dependent on dynamic alterations in the organization of the actin cytoskeleton. A causal relationship between gelsolin expression and in vitro invasion by way of signaling through Ras has been reported.