The Western Indian Ocean Palythoa liscia Haddon and Duerden has been found to contain three cell growth (PS) inhibitory proteins with molecular weights ranging from 128,000 to >2×10⁷. The lowest mass protein from this colonial Zoanthiniarian, palystatin 1 (PS, ED50 1.3-5.5×10⁻⁴ pg/ml) may be a subunit of the two high mass cytotoxic (PS, ED50 0.01 pg/ml) proteins palystatins 2 and 3. Isolation of palystatins 1-3 was guided by bioassay (PS in vitro) through a sequence of gel permeation chromatographic methods utilizing Sephadex LH-20 to Sepharose 4B.