AbstractChanges in the composition of the outer walls of glasshouse tomatoes during ripening have been studied. The fruit, mainly of the variety ‘Potentate’, was carefully graded by colour into either five or six categories from mature green to red.The content of sugars and total solids in the expressed juices increased significantly from the green to the red stage. The nitrogen content showed little variation from the green to the orange stage, but increased significantly on reaching the fully red condition.The titratable acidity of the juices increased significantly from the green to the green‐yellow stage of ripeness, accompanied by decreasing pH. No consistent changes in acidity could be established after the first appearance of yellow colour, the acidity rising in some series and decreasing in others. A tentative explanation of this behaviour, which differs from that of the juices from the locules and from the whole fruit, is discussed.