1. 1. Tube feet tissues of adult starfish contain a much higher proportion of actin protein than pyloric caeca as shown by SDS-polyacrylamide gel electrophoresis. 2. 2. Hybridization of a cloned chicken beta actin DNA probe to Southern blots of Hind III restricted pyloric caeca DNA revealed a prominent homologous fragment of approx 4.6 kb. 3. 3. Dot hybridization of the cloned chicken actin probe to pyloric caeca and tube feet DNA showed no significant difference in the beta actin gene levels between the two tissues. 4. 4. These results indicate that cloned vertebrate genes can be used to investigate gene expression in asteroids and that the differential expression of actin genes is not due to gene amplification in the tube feet. © 1985.