During the chemical investigation of the seeds of Seseli indioum', W. 8 A., a new product, a.p. 15345'; L-4c_TD 3o + 3o" , was also isolated from the neutral part of the petroleum-ether extract after saponification and steam-distillation. This compound, of composition c29 48 H 0 rC, 84.OOk H, ii.09k Calcd. for Cz9Rr80s C, 84.40%; II, ii.72%_7, b4+ 41% (base peak as well), has been found to contain two oleflnlc linkages and one hydroxyl group. On the basis of extensive studies it has been found to be a new sterol and has been designated as 'Indosterol'. This communication presents the evidence leading to the structure 3/bhydroxy-56-stigmasta-9(ii), 22(23)-dlene (I) for indosterol. The compound was separated and purified by chromatography on alumina and proved homogeneous by thin-layer-chromatography on silloa gel (pure, and with AgN03-20%). It gave positive Liebermann-Burchard and tetranitrorethane tests and indioated a diene system by perbenzoic acid titration. The mass spectrum of the substance revealed oharaoterlstic peaks at m/e 369, 351, 314, 300, 273 (M+-139, the side ahaii), 2'7IL-M*-(139+2)J2, 255, 231, 213, 159, 81, and 43. The mass peak m/e 271 is more intense than the peaks m/e 314 and 273. The NMR spectrum (60 Ml-la) showed the presence of methyl signals at 60.70, 0.75, 0.80, 0.85, 0.90, 0.967, 1.00, and 1.07 (which may be assigned' respectively at oarbon atoms IS; 29; 26, 27; 29; 26, 27 Iyr 29; 21; 19 and 21), secondary carbinol methine ( 6 3.6, broad II , ii%) and oleflnlc protons at 65.12 (dt, 2R) and at 65.35 (dt, IR); )>m-(KBr) 3325, 1650, 1050 and 830 or-l. Treatment of (I) with acetic anhydride and pyridine furnished an