This study was designed to examine effects that access to manipulatives in science instruction have with respect to the development of spatial conceptual abilities and whether the effects were different for males and females. A secondary purpose of this investigation was to examine what relationship sex and access to manipulatives in conjunction with sex has on the development of projective spatial ability. The sample consisted of 52 fifth-grade students. The experimental group received instruction using the Energy Sources unit from SCIIS, while the control group's instruction was designed around a science textbook. Spatial ability data was gathered from both groups utilizing a battery of three Piagetian-type tasks. The study concludes that both males and females benefit from access to manipulatives in the development of projective spatial abilities. (Author/DS)