Amino acid analysis of pure murein isolated from cells of T. neapolitanus revealed the typical constituents of most mureins form Gram-negative bacteria. i.e. glutamic acid, alanine and diaminopimelic acid, but the molecular ratio ot these was unusual, being approximately 1: 1: 1. The reduced amount of alanine was explained by the absence of monomers containing tetrapeptide side chains, as revealed by h. p. 1. c. analysis, [(3)H]glutamic acid, [(3)H]diaminopimelic acid and [(3)H]N-acetylglucosamine were incorporated into the murein and allowed to determine the degree of its crosslinkage (28%) and the occurrence of turnover.