In order to take into account in a more productive, effective manner children's prior science knowledge in the development of science curricula and in the teaching of science, it is important "to know how to explore it, to know about its nature, and to consider the various ways it may, or may not be modified" (Gilbert, Osborne, and Fensham, 1982). Given that many elementary teachers report feeling either ill-prepared or unqualified to teach science, the experience of elementary school students in learning science particularly warrants continued investigation. This study attempts to take a step beyond identification of preservice elementary teachers' science misconceptions in the direction of concurrent characterization of the bases of these ideas. Using a multi-step process of development, revision and validation, an 11-item multiple-choice test exploring the concepts of surface area/volume and states of matter was developed for subsequent use in evaluating and revising a science process skills course for preservice elementary teachers. Each of the items in the test included a description of situation, a multiple-choice question based on the situation, followed by eight to twenty possible explanations for the answer selected. Test results allow the researcher to identify pre-knowledge about the concepts of interest and to characterize the degree of congruence between the learner's school and intuitive sources of knowledge. It is proposed that this and similar concepts tests could be used in evaluating the effectiveness of strategies devised to change misconceptions or to bring learners' school and intuitive knowledge into congruence with other measures of ability or pre-knowledge to explore interactions with different methods of instruction. Sample questions are appended. (Author)