Four 26,27-cyclosterols, aragusterol B (1), xestokerol A (2), 7-oxopetrosterol (3), and petrosterol (4), were isolated from the methanol extract of Xestospongia testudinaria by various chromatographic methods. Their structures were elucidated by spectroscopic methods and comparison of their spectral data with reported values. Compounds 1-4 were isolated from X testudinaria for the ftrst time.