Cream butter and sugar together. Add eggs, one at a time, beating until smooth. Blend in mashed bananas.
In second bowl, stir flour with baking soda, baking powder, salt and nuts. Add to banana mixture stirring only to moisten. Transfer to greaded loaf pan. Bake in 350 degree oven for about 1 hour, or until a toothpick inserted in the center comes out clean. Let stand 10 minutes. Remove from pan and place on cake rack to cool. Wrap to store.