Ring shake is a wood defect that occurs very frequently in sweet chestnut (Castanea sativa Mill.). By examining this particular kind of wood failure it is apparent that, at an anatomical level, separations occurring in the wood tissue show different features. In order to collect further information to help in understanding the causes that lead to the development of ring shake, a microscopic description and a quantification of these different ring shake typologies has been performed on 45 chestnut wood discs. Results showed that among the various shake types encountered, the crack-form, i.e. the failure that develops across the earlywood cell walls, is largely the most frequent and is principally found in fresh felled wood. Detailed observations reinforce the belief that the set off mechanism leading to crack-failure is related to the combined interaction of the structural weakness of chestnut wood with growth stresses developed in the stem.