The high response of our isolate of Streptomyces griseoviridus was exploited to provoke the synthesis of new viridogrisein homologues by adding various amino acids to the culture medium in an attempt to replace the alanine, sarcosine, leucine and phenylsarcosine moieties of virdogrisein. Among the amino acids added, L- and DL-alpha-amino-n-butyric acid and L-methionine gave new TLC spots which we named neoviridogriseins I and III and neoviridogrisein VII, respectively. The structures of neoviridogriseins I and III were elucidated: In both compounds, the alanine moiety of viridogrisein is replaced by a L-alpha-amino-n-butyric acid residue; furthermore, in neoviridogrisein I, the allo-hydroxy-D-proline is replaced by D-proline.