A thermophilic bacterium was isolated from a hot spring area of Yellowstone National Park. The organism grew optimally at 60-65 degrees C and in the pH range of 6-9. It was characterized as Bacillus sp. In the presence of corn or olive oil (1.0%) as the growth substrate, this Bacillus produced an extracellular lipolytic activity (EC 3.1.1.3). The enzyme activity could be efficiently recovered by ultrafiltration of cell-free culture supernatant. The partially purified lipase preparation had an optimum temperature of 60 degrees C, at an optimum pH of 9.5. It retained 100% of the original activity after being heated at 75 degrees C for half an hour. The half life of the enzyme was 8 h at 75 degrees C. The enzyme retained at least 90% of tie original activity after it was incubated at 60 degrees C for 15 h at pH’s in the range of 5 to 10.5. The enzyme was active on triglycerides containing fatty acids having a carbon chain length of C16:0 to C22:0 as well as on natural fats and oils. The enzyme activity was stable to both hydrogen peroxide and alkaline protease which are detergent ingredients. The purified enzyme had an isoelectric point of 5.15 and an approximate molecular weight of 65,000.