Malformin A, produced by Aspergillus niger, was analyzed on HPLC equipped with C- 18 reverse phase column, and four peaks were detected. Two of them were assigned for AI and A2 by amino acid analyses and mass spectra. Their structures were dedoced for cyclic pentapeptides by two dimensional NMR experiments as cyclo-D-c~teiny~-D-c~teinyl-L-valyl-D-leucyl-L-isoleucyl for Al and Cyclo-D-cysteinyl-D-cysteinyl-L-valyl-D-leu~l-L-v~~ for AZ. Malformins, a family of metabolic products of AspergMus niger, induce root curvatures on corn plants and malformations on bean plants 1. They also have antibacterial* and cytotoxic propertiess, and stimulate plant growth 4. Malformins were isolated from culture fluid of A. niger which produced At and A25 by strain 56-39, Bt and Bss by strain 56-30, and C by strain AN-l '.The structures of malformin Ats and C7 were elucidated by both chemical synthesis and degradation. The structures of other malformins have never been previously determined, because they are difficult to separate on either paper or silica gel chromatography. Preparative HPLC and two dimensional NMR experiments have been applied on the structural elucidations of malformins. In this communication, we will describe the structure of malformin A2 and spectrometric analysis of AI.