Reported are results of a study designed to determine developmental patterns in proportional reasoning and to determine if these patterns are similar regardless of educational level and regardless of problem context. Data from 2282 subjects in grades 6-13 were collected using the Test of Logical Thinking (TOLT), and then examined for subjects who had been categorized in three ways: (1) by TOLT scores, 1-10; (2) by educational level; and (3) by developmental stages within each educational level. Examination of the four most common responses indicates that observed patterns of reasoning are similar regardless of developmental level, educational level, or problem context. Conclusions are made regarding the use of proportional reasoning in the physical sciences and biological sciences. (CS)