1. Preheat oven to 350F, grease 9x5x3" bread pan.
2. Cream butter and sugar till light and fluffy. Add eggs one at a time, beating well after each addition.
3. Sift all purpose flour, baking soda and salt together, stir in whole wheat flour and add to creamed mixture, mixing well.
4. Fold in bananas, vanilla and walnuts.
5. Pour mixture into pan, bake 50 to 60 mintes or till cake tester comes out cleancool in pan 10 minutes, then on rack. Makes one loaf.