In every school there are bright, motivated students who experience success in every field of academic endeavor except mathematics. These students are defined as dyscalculics, or learning disabled in mathematics. Piaget's model for cognitive development was used in a study of students evidencing this condition. The purpose of the study was to compare cognitive development as measured by the ability to conserve length, area, and volume in two groups of seventh-grade students. The groups consisted of students of average or above average intelligence who (1) evidenced learning disability in mathematics but who performed well in reading (N=30) and (2) those who performed well in both subjects (N=30). Subjects were selected from seventh-graders in the Shelby County, Alabama, school system. A comparison of selected factors indicated different maturation levels between the dyscalculic and control groups. Results indicate that the proportion of students who could conserve volume in the dyscalculic group to be significantly less than the proportion of conservers in the control group. Further, sex differences were found among control pupils with nearly 89 percent of the males but only 50 percent of the females capable of conserving volume. Data are seen to support previous findings that conservation is essential to mathematical success. (Author/MP)