A novel phenazine derivative (1) together with six known compounds (2-7) were isolated by bioassay-guided fractionation from the culture broth of a bacterium, Bacillus sp., collected from a Pacific deep sea sediment sample (depth 5059 m). The structures of these compounds were determined using spectroscopic methods. Their cytotoxic effects on P388 and K562 cell lines were preliminarily examined using the sulforhodamine-B (SRB) assay.