A pink carotenoid pigment was separated by column chromatography from the red, autumnal leaves of plants belonging to the family, Taxodiaceae. The results of analytical studies on this pigment may be summarized as follows: 1. One and the same pink carotenoid pigment was found in red, autumnal leaves of 9 genera of Taxodiaceae in common. 2. The pink pigment was identified as rhodoxanthin, which belongs to the group of xanthophyll. 3. The color change from green to red occurring in autumnal leaves of taxodiaceous plants is due to the formation of rhodoxanthin. 4. As the synthesis of rhodoxanthin proceeds in leaves, other carotenoids, especially carotenes, seem to decrease in amount.