Elongation, fresh and dry weights of muskmelon seedlings (Cucumis melo cv. Kis kavunu) were enhanced by juglone in intact seeds. In the case of coatless seeds, root elongation decreased but fresh and dry weight of the seedlings were increased by juglone. While protein content was slightly increased by juglone in cotyledons of intact seeds, it did not change significantly in coatless seeds. Catechol oxidizing activity of polyphenol oxidase (PPO) enzyme increased in cotyledons of juglone treated intact seeds whereas it did not change significantly in coatless seeds.