When total phenol content was assayed in ripening tomatoes results were often contradictory, since it changed differentially depending on the cultivars (Ilahy et al., in press) or it remained pretty stable (Helyes and Lugasi, 2006). Our results (Table 1) show that, in watermelon, the amounts of total phenols and flavonoids significantly change during ripening (P < 0.05). The highest amount of phenols and flavonoids was usually detected at the red-ripe stage in all the studied cultivars, with the exception for Giza and P403 cultivars.