A specific, sensitive bioluminescence assay for myo-inositol is described employing myo-inositol dehydrogenase linked to a commercial NADH bioluminescence kit. Optimum conditions providing a linear response over 4 orders of magnitude are presented with reproducibility of 6% CV and a sensitivity of 1 pmol. The assay is suitable for the measurement of inositol at low concentrations or in small volumes.