The study investigated the determinants of economic efficiency among Hoaloc-mango growers in Vietnam.  The result revealed that the mean economic efficiency of the cooperative farmer group was greater than that of the non-cooperative farmer group in seasons 1, and 2, and less than in season 3. The positive determinants of the economic efficiency of the cooperative farmer group were age, and education in season 1, credit access in seasons 2, and wrapping bag and classifying sale in season 3, while the negative factors were farming experience, credit access, payment for the agro-input wholesaler, market access, classifying sale, plant density in season 1, age, education, credit access, wrapping bag, market access in season 2, and farming experience, credit access, and plant density in season 3. The positive factors of EE in the non-cooperative farmer group were credit access, and plant density in seasons 1, credit access, and market access in season 2, and farming experience, classifying sale, and plant density in season 3. On the other hand, the negative determinants of economic efficiency of non-cooperative farmer group were age, wrapping bag in season 1, education, farming experience, and classifying sale in season 2, and age, education, and payment for the agro-input wholesaler in season 3.

Key words - Economic efficiency, cooperative, non-cooperative