In the course of a continuing study on the free amino acids profile of seaweeds, several amino acids hitherto undetected were isolated from the thalli of the calcareous red algae Serraticardia maxima (Yendo) Silva. One of which appeared at tR 79 (min) on an amino acid analyzer and the 440 to 570 nm absorption ratio of the ninhydrin product was 4.2. This value is similar to that of imino acids and related compounds. The compound was purified by several liquid chromatographic procedures from the hot alcohol extract of algae and identified as L-baikiain (L-1,2,3,6-tetrahydropyridine-2-carboxylic acid). In the present paper, the procedures used for the structural elucidation of this compound from small sections of the thalli of marine algae are described. Also, the distribution of this compound among seaweeds, especially those related to calcareous red algae, is discussed.