The objective of the project was to determine the composition of particular sugars and starch during development of cotton (Gossypium hirsutum L.) flower bud (square) and flower. The nonstructural carbohydrate composition was determined through late development of first-position squares on Deltapine 50 plants grown in 1997 at Mississippi State University. Soluble sugar, not starch, was the dominant nonstructural carbohydrate component of the buds throughout development. Sucrose hydrolysis, but not starch hydrolysis, contributed to a more negative osmotic potential during rapid petal expansion. There is a sharp decline in soluble-sugar (glucose, fructose, plus sucrose) content of the flower during senescence, possibly due to 1) a respiration climacteric, and 2) remobilization from petals to the young boll or other plant parts.