Abstract: Histochemical studies on the distribution of cytochrome oxidase, polyphenol oxidase, peroxidase, acid phophatase, and adenosine triphosphatase (ATPase) had been carried out on the growing cucurbita stem by the technique of cold free-hand section. The results obtained in this investigation are briefly summarized as following: 1. The activity of these enzymes described above is higher in the vascular bundle than that in the epidermal and ground tissues. 2. All of these enzymes are present in both the companion cells and the sieve cells, but only three of them (polyphenol oxidase, acid phosphatase, and ATPase) are observed in the xylem parenchyma. 3. It is remarkable to note that the cytochrome oxidase, polyphenol oxidase, and acid phosphatase are also demonstrated in the glandular hairs of the stem epidermis. 4. The cytochrome oxidase which is not usually present in the xylem parenchyma cells, may be found to be present in such cells at the areas with higher metabolic rate, such as in the internodes next to the apical meristem and in the pedicels of the female flowers or of the young fruits. 5. In addition to cytoplasm, the peroxidase also appears on the cell wall and on the cytoplasmic membrane. Similar result was obtained by biochemical analysis. The results presented here in this investigation demonstrate clearly that an intensive enzymatic activity does occur in the vascular bundles of the growing stem. This is of significance because it suggests that the presence of these enzymes in such tissue may participate actively in the transportation mechanism of organic substances.