Crucigasterins 277, 275, and 225, three new polyunsaturated amino alcohols, 10-12, were isolated from the Mediterranean tunicate Pseudodistoma crucigaster. The structures of these compounds were assigned based on NMR and FABMS data. Absolute stereochemistry of the amino alcohol portion in 10 was assigned to be 2R,3S based on chiral GC comparison of 3-hydroxy-4-aminopentanoic acid 13d, a chemical degradation product of 10, with a synthetic sample prepared from L-alanine. Compounds 10-12 exhibited moderate cytotoxicity and antimicrobial activity.