In our continuing search for new natural and semisynthetic analogues of the useful anticancer drugs daunorubicin (1a) and doxorubicin (1b), we examined the fermentation broths of Micromonospora peucetica n. sp. and isolated an anthracycline complex. From this complex, we purified and structurally characterized four new biologically active anthracyclines: 11-deoxydaunorubicin (2), 11-deoxydoxorubicin (3), 11-deoxy-13-dihydrodaunorubicin (4), and 11-deoxy-13-deoxodaunorubicin (5). Purification was performed using a silica gel column. Structural determination utilized UV, visible, IR, 1H NMR, and 13C NMR spectroscopy, mild acid hydrolysis (affording the amino sugar daunosamine and four aglycones), preparation of derivatives (e.g., acetyl and O-isopropylidene derivatives), and was confirmed by single-crystal X-ray analysis of the tri-O-acetyl derivative (7) of the aglycone of 2. The X-ray analysis verified the relative configuration and molecular geometry, which closely resembled that of daunorubicin. Biological testing demonstrated that the four new glycosides exhibited in vitro activity against HeLa cell cultures with IC50 values ranging from 0.05 μg/mL (for 2) to 0.44 μg/mL (for 5). In vivo testing on P388 leukemia showed T/C values of 181 for 2 (at 100 mg/kg) and 245 for 3 (at 66 mg/kg), compared to doxorubicin's T/C value of 213 (at 6.6 mg/kg).