In this study, the bacteria which were isolated from various milk and fermented food products were tested for their ability to convert metmyoglobin to nitrosomyoglobin. Lactic acid bacteria were isolated from samples of raw milk, unsalted butter, Beyaz cheese, yoghurt, pickles and silage. The nitric oxide (NO) forming abilities of 1534 isolates were tested using plates of de Man, Rogosa, Sharpe agar supplemented with metmyoglobin (MRS-Mb). Ten isolates formed bright red colonies, brown or clear zones due to the conversion of metmyoglobin to nitrosomyoglobin were identified. Five of the 10 bacteria were identified as Lactobacillus plantarum, three as Pediococcus acidilactici, and two as Leuconostoc mesenteroides subsp. dextranicum. NO formation ability was measured in MRS-Mb broth. There were differences not only among the species, but also among the strains of a species. The highest NO concentrations of 51.5, 51.3, 50.2 mu M were produced by P. acidilactici S2, L. plantarum T119, and P. acidilactici S3, respectively.