Three cyclopentanepentols have been synthesized: the 1,2,4/3,5-isomer by acid hydrolysis of an anhydro-cyclopentanepentol, DL-1,2-anhydro-4,5-O-cyclohexylidene-1,2,3/4,5-cyclopentanepentol; the 1,2,3/4,5-isomer by deamination of (1,4/2,3,5)-5-amino-1,3-di-O-acetyl-2,3-O-cyclohexylidene-l,2,3,4-cycopentanetetrol; and the 1,2,3,4/5-isomer by solvolysis of two tetra-O-acetyl-O-tosylcyclopentanepentols. An equilibrium mixture of the three cyclopentanepentols was obtained by heating one of them with 95% acetic acid in the presence of a strong acid. The relative stabilities of the three isomers are in the order 1,2,4/3,5 > 1,2,3/4,5 > 1,2,3,4/5.