Sift together flour, baking powder, soda, and salt.
Set aside.
Creambutter and gradually beat in sugar until light and fluffy.
Beat in eggsone at a time.
Add flour mixture and banana alternately in three parts.
Gently stir in blueberries.
Turn into oiled 9 x 5-inch loaf pan.
Bake at350 degrees for 50 minutes.
Turn out of pan to cool.
Makes 1 loaf.