<jats:title>Abstract</jats:title><jats:p>Two new ceramide lactosides, acanthalactoside A (<jats:bold>1</jats:bold>) and B (<jats:bold>2</jats:bold>) were isolated from the water‐soluble lipid fraction of the chloroform/methanol extract of the starfish <jats:italic>Acanthaster planci.</jats:italic> On the basis of chemical and spectral evidence, the structures of <jats:bold>1</jats:bold> and <jats:bold>2</jats:bold> were characterized as 1‐<jats:italic>O</jats:italic>‐[β‐<jats:sc>D</jats:sc>‐galactopyranosyl‐(1→4)‐β‐<jats:sc>D</jats:sc>‐glucopyranosyl]‐substituted (2<jats:italic>S</jats:italic>,3<jats:italic>S</jats:italic>,4<jats:italic>R</jats:italic>)‐2‐[(2<jats:italic>R</jats:italic>)‐2‐hydroxytetracosanoylamino]‐1,3,4‐hexadecanetriol (<jats:bold>1</jats:bold>) and (2<jats:italic>S</jats:italic>,3<jats:italic>S</jats:italic>,4<jats:italic>R</jats:italic>,13<jats:italic>E</jats:italic>)‐2‐[(2<jats:italic>R</jats:italic>)‐2‐ hydroxyhexadecanoylamino]‐13‐docosene‐1,3,4‐triol (<jats:bold>2</jats:bold>), respectively. Reversed‐phase column chromatography was useful to obtain the glycosphingolipid mixture from the watersoluble lipid fraction containing also other material such as steroid saponins. Reversed‐phase HPLC was also effectual to isolate these ceramide dihexosides reveling very close resemblance in structure. Negative FAB mass spectrometry was successfully used for the determination and confirmation of the ceramide dihexosides.