The estimated quantity of rice straw and its use in some provinces in the Mekong Delta region was carried out based on prepared questionnaires and field surveys in An Giang, Dong Thap, Kien Giang and Can Tho. The results showed that there were six common methods of rice straw treatment. They include burning, burying, mushroom cultivation, breeding, sale and giving away. The methods of using rice straw vary depending on the rice season crops. In the Winter - Spring season, burning is the most common method (98.2 %), whereas mushroom cultivation and sale are the least. In the Summer–Autumn season, the proportion of straw burning decreases to 89.67 %, and that of burying to 6.65 %. In the Autumn–Winter season, straw burning has the lowest level (54.1 %), and the proportion of straw burying is quite high (26.1 %), followed by mushroom cultivation (8.14 %) and the rest methods share the small proportions. The estimated quantity of rice straw in the Mekong Delta region is approximate 26.23 million tons annually, in which 20.93 million tons is burned directly on the fields. This practice releases into the atmosphere with about 17.95 million tons of CO₂, 485.58 thousand tons of CO and 10.38 thousand tons of NO_x. The results also show that most farmers tend to continue the practice of burning straw as the most popular method in the next few years.