Content and composition of free sterol (St) and sterol esters (SE) of cotton and sunflower seeds during maturation were investigated. Regarding cotton seed, sterol composition of the both type lipids was examined for the anatomical parts (cotyledons, embryo and seed coat). The two types of lipid isolated from the seed lipids by preparative-TLC were analyzed by GLC, respectively. However, bef ore GLC analysis, SE was hydrolyzed in methanolic KOH. The relative percentage of unsaponificable matter and 4-demethylsterol of cotton and sunflower seed was greater at an earlier stage of flowering than those at any other growth stage. With the growth af cotton seed, the relative percentage of sitosterol and campesterol of the two types of lipid increased and then decreased. There were clear differences in sterol composition between St and SE during maturation of these seeds. The relative percentage of cholesterol and campesterol vf SE was greater than those vf St, and that of the former was considerably great in the seed coat of cotton seed.