This study explored the effects of a left-hemispheric, right-hemispheric, or integrated teaching approach on students' achievement and attitudes. One hundred eighteen second-grade pupils were randomly assigned to four groups to receive two weeks of instruction on geometry and measurement with: (1) a formalized, structured-textbook approach; (2) a variety of hands-on, manipulative activities without use of a textbook; (3) a textbook and manipulative approach; or (4) no instruction on the mathematics unit. Half of the pupils took the pretests and half took the posttests. The greatest gain in achievement and attitudes occurred with the manipulative approach (right hemispheric), while the textbook approach (left hemispheric) resulted in the least gains. (MNS)