Carpetimycins A and B, two new carbapenem antibiotics related to thienamycin, olivanic acid derivatives, and PS-5, were isolated from the culture filtrate of Streptomyces sp. KC-6643. The strain was cultured in a medium composed of starch, soybean meal, cotton seed oil, and inorganic salts, followed by fermentation in a 200-liter fermentor. The antibiotics were purified through processes including adsorption on Diaion PA-306, desalting on Diaion HP-20, column chromatography on Amberlite IRA-458, QAE-Sephadex A-25, Sephadex G-10, and final purification via HPLC to obtain pure carpetimycins A (39 mg) and B (210 mg) as sodium salts. Carpetimycin A sodium salt is a colorless solid melting above 145°C with decomposition, [α]24D -27° (c 1.7, water), showing UV maxima at 240 nm (E1%1cm 369) and 288 nm (E1%1cm 300), IR peaks at 1770, 1695, 1625, and 1265 cm-1, 1H-NMR data, FD Mass (MH+ of methylester at 357), and molecular formula C14H18N2O8S. Carpetimycin B disodium salt is a colorless solid melting above 130°C with decomposition, [α]24D -145° (c 1, water), showing UV maxima at 240 nm (E1%1cm 357) and 285 nm (E1%1cm 305), IR peaks at 1770, 1695, 1625, 1270-1220, and 1050 cm-1, 1H-NMR data, and molecular formula C14H18N2O9S2. Both antibiotics are more stable than olivanic acid derivatives, with half-lives of 187 hours (A) and 170 hours (B) in McIlvaine's sodium phosphate-citric acid buffer (pH 7.0) at 25°C. They exhibit strong activity against Gram-positive and Gram-negative bacteria, including β-lactamase-producing strains, with carpetimycin A being 8-32 times more active than B. They also show inhibitory activity against β-lactamase. Their structures, including stereochemistry, were elucidated via spectral data, conversion of carpetimycin B to A, and X-ray crystallographic analysis of carpetimycin A p-bromobenzyl ester.