A geometrical isomer composition excellent in odor and in chemical resistance, which is applicable to a base material containing a strongly alkaline chemical or a strongly acidic chemical, which can suppress the deterioration with time and the color change of the base material in the case that the material is exposed to light, and which also have highly tasteful and unique fruity floral fragrance. A geometrical isomer composition containing 93 to 99% by weight of optically active trans-1-(2,2,6-trimethylcyclohexyl)-2-buten-1-one represented by Formula-1 or a mixture thereof and 7 to 1% by weight of optically active cis-1-(2,2,6-trimethylcyclohexyl)-2-buten-1-one represented by Formula-2 or a mixture thereof is, respectively, used ##STR1##