Strains of Bacillus circulans produced the new aminoglycoside antibiotics 4'-deoxybutirosins A and B (Bu-1975C1 and C2). The new antibiotics (C21H41N5O11) have physicochemical properties similar to butirosins A and B (C21H41N5O12) with specific differences in TLC and NMR. Bu-1975C1 is 4'-deoxybutirosin A composed of D-xylose, 2-deoxystreptamine, L-(-)γ-amino-α-hydroxybutyric acid and 2,6-diamino-2,4,6-trideoxy-D-xylo-hexopyranose (a new deoxy amino sugar), while C2 is 4'-deoxybutirosin B containing D-ribose instead of D-xylose of C1. The antibacterial activity spectra of 4'-deoxybutirosins are broader than that of kanamycin and butirosins, inhibiting some kanamycin and/or butirosin-resistant organisms and showing increased anti-pseudomonal activity. The acute intravenous toxicity of Bu-1975C1 is lower than that of kanamycin and similar to butirosin A. This paper reports on the producing organism, fermentation, isolation and the physicochemical and biological properties of Bu-1975C1 and C2.