A new form of the Purdue Elementary Problem Solving Inventory which presents real-life problem situations as three-dimensional models is described and developmental data is presented. Second and fourth graders in an advantaged and a disadvantaged school were given either the model version or the original slide version of the Inventory. The model version was found to be an internally consistent, equivalent form of the original Inventory. The KR-20 for the combined sample was .64 for both the model and the slide versions. Also, a coefficient of equivalence for students taking both forms of the Inventory was .73. (Author)