Aerobic growth of 22 strains of lactic acid bacteria of the genera Lactobacillus, Pediococcus, Leuconostoc, Streptococcus, and Enterococcus was investigated. Most strains grew well under aerobic conditions in parallel with an increase in the growth yield. Homofermentatives and heterofermentatives produced acetic acid under aerobic conditions with a decrease in lactic acid or ethanol in the culture medium. NADH oxidase and NADH peroxidase activities were detected in a wide variety of the bacteria. Most strains showed the activity of NADH oxidase that produced water, acid some strains showed the activity of NADH oxidase that produced hydrogen peroxide. L. delbrueckii subsp. delbrueckii NRIC 1053 and L. fermentum H3 and Y6 accumulated hydrogen peroxide in the culture medium, and these strains grew poorly under aerobic conditions, which might have been due to hydrogen peroxide toxicity. The hydrogen peroxide was eliminated by the addition of catalase to the culture medium. The activities of NADH oxidase and NADH peroxidase were enhanced by the addition of FAD to the reaction mixture. A possible role of FAD in the reaction was discussed.