A strain of Bacillus subtilis was able to grow and produce a biosurfactant on 2% sucrose at 45C. As a result of biosurfactant synthesis the surface tension of the medium was reduced from 68 dynes cm1 to 28 dynes cm1. The strain had the capacity to produce the biosurfactant at high NaCl concentrations (4%) and a wide range of pH (4.510.5). The biosurfactant retained its surface-active properties after heating at 100C for 2h and at different pH values (4.510.5). A maximum amount of biosurfactant was produced when urea or nitrate ions were supplied as nitrogen source. The use of the biosurfactant at high temperatures, acidic, alkaline and saline environments is discussed. As a result of its action, 62% of oil in a sand pack column could be recovered, indicating its potential application in microbiologically enhanced oil recovery.