A new member of the surfactin family of microbial lipopeptides has been isolated from the cell broth of Bacillus subtilis TD 7 by reverse phase high performance liquid chromatography (RP-HPLC), and identified by FT-IR, GC-MS, LC-MS/MS, H-1-NMR and C-13-NMR. The surfactin-C-11 consists of a heptapeptide with the sequence of N - Glu - Leu - Leu - Val - Asp - Leu - Leu - C, and a beta-hydroxy fatty acid chain with 11 carbons, which is a new member with the shortest hydrophobic chain among the surfactin family produced by B. subtilis. The critical micelle concentration (CMC) of the surfactin-C-11 is 5.59 x 10(-5) mol/L in 10 mmol/L phosphate buffer solution (PBS, pH 7.4) at 25 degrees C, and the surface tension at CMC (gamma(CMC)) is 34.42 mN/m. The hemolytic activities of the surfactin-C-11 on 2 % defibrinated sheep blood showed a HC(50 )of 448.51 mu mol/L. Surfactin with short fatty acid chain has low toxicity on erythrocyte, which implies potential applications in biotechnological and pharmaceutical fields.