This paper reviews some literature on the emergence of formal reasoning and reports a study of reasoning performance of 213 middle grade students in relationship to grade level and chronological age. While a number of large-scale studies have indicated that formal reasoning emerges in a regular progression across age ranges and grade levels, few researchers have analyzed the role of chronological maturation with smaller, school-related populations. Results of this investigation with such a population reveal no significant associations between chronological maturation and reasoning performance. These findings underscore the complexity of reasoning development and suggest a need for middle grades educators to avoid global generalizations regarding such development. (Author/JAZ)