Bacillus megaterium ALA2 NRRL B-21660 has been well studied for the production of many oxygenated unsaturated fatty acids from linoleic acid. Its major product, 12,13,17-trihydroxy-9(Z)-octadecenoic acid (12,13,17-THOA), inhibited the growth of many plant pathogenic fungi. However, we have been unable, until now, to demonstrate 12,13,17-THOA production in a fermentor. Here, we have investigated the effect of surfactants on 12,13,17-THOA production. Surfactant types (SO-25, Tween-80 and Triton X-100) at various concentrations were evaluated for their effects on cell growth and production of 12,13,17-THOA. Triton X-100 decreased cell growth and 12,13,17-THOA production while 1% Tween-80 increased 12,13,17-THOA production more than twofold over control. In a pH and dissolved oxygen (DO) controlled fermentor and with 1.0% Tween-80, both 12,13,17-THOA production and productivity increased to 553 mg/L and 24.0mg/L/hour, respectively. We further conducted THOA production in a fermentor without the control of pH and DO, but with aeration through medium surface rather than by Spurger, and with various amounts of Tween-80 to compare with the results obtained in flask runs. Both additions with 0.1% and 0.5% Tween-80 and the control runs produced poor amounts of product 12,13,17-THOA. The maximum 12,13,17-THOA production was observed at 1.0% Tween-80 at a yield of 650 mg/L. Thus fermentor production of 12,13,17-THOA was successfully demonstrated.