The free and bound sterols of the marine algae Laminaria saccharina, Ascophyllum nodosum, and Furcellaria fastigiata, were isolated and identified by using a combination of TLC, GLC, and mass spectroscopic techniques. Preparative TLC enabled the fast, efficient separation of each sterol from the mixture for positive identification by GLC and mass spectroscopy. The chromatographic techniques employed permitted the detection and isolation of the more polar sterols in the presence of the more common 3β-monohydroxy sterols. To the authors' knowledge, this is the first recorded detailed sterol analysis of L. saccharina and the first recorded isolation of saringosterol and 24-ketocholesterol from Laminaria. The mass spectra for these two sterols are presented.