A recently recognized group of glycerolipids called betaine lipids, which are composed of diacylglycerol and <I>N</I>-permethylated hydroxyamino acids, are widely distributed in lower plants and algae as well as in some non-photosynthetic microorganisms. The present state of knowledge of the phylogenetic distribution, the fatty acid composition, the thermal properties, and the biosynthesis of the betaine lipids is reviewed in the perspective of a future sought for their biological roles and activities.