Freeze-dried powdered preparations of whole (i.e. without shell) green-lipped mussel (Perna canaliculus) from New Zealand given orally to rats showed some modest anti-inflammatory activity (carrageenan paw oedema). This material strikingly reduced the gastric ulcerogenicity of several non-steroid anti-inflammatory drugs in rats and pigs. The gastroprotective activity in rats was primarily associated with particular lipid fractions, which exhibited differential protective activity against acetylsalicylic acid on the one hand and indometacin on the other.