1) By analysis of bamboo-shoot (higher, middle and lower portions) and matured bamboo, following results were found: i) The contents of extracts and ash were higher in bamboo-shoot than those of matured bamboo. ii) The contents of cellulose, pentosan, lignin and methoxyl in lignin increased along with lignification, but only pentosan content decreased again in matured bamboo. 2) Investigating the change of molecular ratio of lignin building units by alkaline nitrobenzen oxidation, it was found that considerable amounts of p-hydroxyphenyl and guaiacyl nucleus were contained but syringyl nucleus was less contained in the lignin of early lignification stage, whereas, when lignification more progressed the contents of guaiacyl and suringyl nucleus increased and in contrast with bamboo-shoot, the content of syringyl nucleus was highest and followed by guaiacyl and p-hydroxyphenyl nuc leus in matured bamboo. 3) The mean molecular weight of dioxane lignin obtained from the above mentioned samples were lower in early lignification stage than those of matured bamboo, whereas the content of free phenolic hydroxyl was higher in the lignin of former than the latter. 4) The shape of ultraviolet absorption spectra of dioxane lignin in early lignification stage was less clear comparing with that of matured bamboo, but the absorption maximum shifted slightly toward longer wave length than that of matured bamboo. 5) From the above mentioned results it was considered that the increase in methoxyl content of the lignin at the successive stage of lignification was ascribed mainly to the increase of higer methoxyl containing building units but partly to the humic substance accompanied with isolated lignin of less lignified material.