Microorganisms represent a well-documented source of herbicidal compounds with the potential to provide agricultural researchers with new structural classes for herbicide synthesis efforts1*. In the continuation of a screening program to discover novel natural product herbicides from microbial sources2), Streptomyces rochei A13018 was found to produce cis-2-amino-l-hydroxycyclobutane-l-acetic acid (CBAA: 1), which causes L-cysteine or L-methionine-reversible chlorosis in Arabidopsis thaliana. CBAA is a constituent of the naturally occuring antibacterial dipeptide (l S,2£> l -hydroxy- 2-[(5)-valylamino]cyclobutane-l-acetic acid (2)3), and has been reported synthetically by Baldwin et alf^. However,no previous reports cite the isolation of CBAA as the free amino acid or describe its herbicidal properties. This note briefly describes the producing organism, fermentation, isolation, structure identification, and biological activities of CBAA.