8"-Hydroxypactamycin and 7-deoxypactamycin, new members of the pactamycin group of antibiotics'-3', were found in culture filtrates of the microbial strain SIPI-A3-0121, which had been isolated by the Shanghai Institute of Pharmaceutical Industry and confirmed to belong to the genus Streptomyces. These antibiotics were isolated and their structures determined by NMR and MS studies. In this communication, the isolation, properties, structure, and biological activities of 8"-hydroxypactamycin and 7-deoxypactamycin are reported.