SUMMARYDeveloping pineapple fruit were analyzed at weekly intervals, two lots in 1958 and four lots in 1963. Both spring and summer harvests were included. Soluble solids, sucrose, reducing sugars, titrable acids, pH, citric acid, and alcohol‐insoluble solids in the flesh show consistent patterns of change during fruit development. The soluble solids and pH of the shell tissues also relate to fruit development, but differ from those in the flesh tissues. By contrast, malic acid and ascorbic acid appear to vary in association with short‐term weather conditions, not with stage of fruit development. The trends in carbohydrate and acid constituents of pineapple fruit suggest several discrete physiological stages: prematuration; maturation, beginning about seven weeks before normal ripeness; ripening, beginning two to three weeks before the half‐yellow stage of ripeness; and senes