AbstractInformation has recently been obtained, mainly with the aid of radioactive compounds, about the biosynthesis of various cyclitols. It was found that the most widely occurring cyclitol, meso‐inositol, is biosynthesized by a pathway probably common to all organisms, in which the cyclohexane ring is formed by ring closure between the two terminal carbon atoms of D‐glucose. Cell‐free extracts or enzyme systems that catalyse the conversion of D‐glucose into meso‐inositol can be prepared from various biological materials. The biosynthesis of the other hexahydroxycyclohexanes (inositols) involves meso‐inositol as an intermediate. A few steps in the conversion of meso‐inositol into other inositols have been studied.