The in vitro degradation of the herbicide bromoxynil at the 25 ppm level by a flexibacterium, strain BR4, was investigated. The degradation was monitored using gas-chromatographic and spectrophotometric analytical procedures. Breakdown was rapid with only 5% of the original herbicide remaining after 5 weeks. No detectable degradation occurred in sterile medium.Thin-layer chromatographic techniques were used to isolate and identify 3, 5-dibromo-4-hydroxybenzamide and 3, 5-dibromo-4-hydroxybenzoic acid as degradation products. A third metabolite was isolated but not identified.