This paper is a qualitative case study designed to identify prospective science teachers' mathematical-logical structures on the basis of their knowledge and achievement levels in magnetism. The study also made an attempt to reveal the effects of knowledge-level variables and procedural variables, which were considered to be potential factors, on the teachers' knowledge and achievement levels. The participants' knowledge level was represented by the APS score (knowledge-level variable), whereas their achievement level was expressed by the ASS score (achievement level). The prospective teachers' knowledge and achievement levels in mathematical logic were 0.204 and 0.305, respectively. The knowledge-level variables were given-asked, formula, and operation. On the other hand, the procedural variables consisted of formula knowledge, basic math knowledge, and scientific knowledge. The latter group of variables had the following values, respectively: 0.336, 0.758, and 0.199. The findings indicated that basic math knowledge led the participants to have an achievement level higher than their knowledge level. The other variables had values similar to those of the knowledge and achievement levels.