The need for an objective index of language development has long been recognized, and various means of measuring language growth have been proposed. This study compares two of the indexes that have recently been devised for measuring language growth. Its specific purposes are (1) to examine the correlation between mean T-unit length and syntactic density scores and (2) to compare mean T-unit length and syntactic density scores as indicators of the grade level of writers. Thirty-two ninth graders were asked to write a composition about the best or worst hour of their day. These compositions were then analyzed for mean T-unit length, mean clause length, and mean number of clauses per T-unit, and were also analyzed for the items needed to compute the syntactic density score. It was concluded that, in spite of its lack of precision, T-unit length is a more useful and usable index of syntactic development than the syntactic density score; and it appears that mean T-unit length is a better indicator of grade level than is the syntactic density score. (RB)