An alkalophilic actinomycete, strain OPC-15, which was isolated from a soil sample, produced phenazine antibiotics in the mycelium. From the results of taxonomic studies, this strain was designated as Nocardiopsis dassonvillei OPC-15. N. dassonvillei OPC-15 produced different phenazine antibiotics under different culture conditions (incubation period, incubation temperature and temperature shift). 1,6-Dihydroxyphenazine (III) was obtained from the mycelium on incubation for 6~8 days at 27°C, while 1,6-dihydroxyphenazine 5,10-dioxide (I, iodinin) was isolated on incubation for 6 days at 27°C followed by further incubation for 2 days at 4°C. 1,6-Dihydroxyphenazine 5-monooxide (II) was purified from the mycelium cultured under both these two sets of cultural conditions. These results suggest that the N-oxidation of III was catalyzed enzymatically with the temperature shift from 27°C to 4°C. In the course of our screening program for new antibiotics produced by alkalophilic actinomycetes, Nocardiopsis dassonvillei OPC-15, which showed temperature-dependent phenazine antibiotic synthesis, was isolated from a soil sample collected in Mino City, Osaka, Japan. This strain accumulated phenazine antibiotics in the mycelium. The present paper describes the production and isolation of these phenazine antibiotics, and effects of the cultural conditions on this phenazine antibiotic producing strain, Nocardiopsis dassonvillei OPC-15, are also reported.