Cream butter; gradually add sugar, beating until light and fluffy. Add eggs, one at a time, beating well after each addition.
Sift together flour, baking powder, and salt; repeat sifting, and add to creamed mixture alternately with milk, beginning and ending with flour mixture. Mix just until blended. Gently stir in pecans and vanilla.
Spoon batter into a greased 8 1/2- x 4 1/2- x 3-inch loaf pan. Bake at 350° for 1 hour or until wooden pick inserted in center comes out clean. Cool in pan 10 minutes; remove from pan, and cool completely on wire rack.