Banana cultivation is considered one of the most important agricultural activities of economic and socialrnimportance in Ethiopia. The objective of this work was to investigate minerals, reducing sugar, resistantrnstarch and polyphenol oxidase activities of fi veselected banana varieties, these are giantrncavendish,butuza,robusta,poyo and williamsofEthiopia. Banana fruits were collected, dried, ground andrnashed. The mineral elements potassium(K), Iron (Fe) and zinc(Zn) were analyzed. Their composition wasrnfound to be 0.627 - 1.047 mg!IOOg for iron, 0.217 - 0.307 mg! IOOg for zinc and 287.171 - 355.271rnmg! I OOg for potassium inripe banana fruits. Bananas are considered a good source of K in the diet, andrnthe data obtained herein support these assertions. Zn and Fe are other minerals of nutritional importancernin bananas and this study has shown that their average values are adequate to support its nutritive value atrnripening stages.The RS content of banana were between 52.2 - 61.4 g! IOOg that containing the highestrnamount of RS, banana has a higher RS content the highest value comingfrompoyo fo llowed by GiantrnCavendish.For reducing sugar, the sample extract was filtered through the two layers of cloths and reextractedrnin hot 80% alcohols. using 2 to 3 ml of alcohol per gm of sample and tested by Fehling'srnsolution. The precipitate and color change of the sample were calculated by titration method andrnPolyphenol oxidase has been shown to be responsible for browning reactions and discoloration in bananarnfruit. Polyphenol oxidase was indirectly iso lated. The activity of the enzyme was evaluated usingrnHallberg and Halthen's algorithm method. Banana PPO catalyzes oxidation of both various substratesrnwith catechol being the most readily oxidized substrate. The optimum pH of the enzyme was between pHrn6 and 7 for all cultivars. Banana polyphenol oxidase was active towards catechol but not withgalloyl.Thernresult obtained in this study showed that banana fruits can be a potential source of mineral elementsrnsupplement in the diet especially for k, and good source of resistant starch and reducing sugar.rnKey words: Banana, mineral,reducing sugar, resistant starch and polyphenol oxidase