In order to determine the effects of writing for different audiences and in different modes of discourse on the syntactic complexity of compositions written by sixth and tenth grade students, 240 students were asked to write in three different modes (argumentive, descriptive, and narrative) to be read by a teacher and a best friend. There was a significant audience effect on clause length for the 120 tenth grade students whose compositions written for the teacher were more syntactically complex than those written for the best friend. At both the sixth and tenth grade levels, the argumentive mode was more syntactically complex than either the descriptive or narrative modes. The results indicate that narrative writing, which showed no increase in syntactic complexity over a four year age span, is not useful for examining the development of syntactic complexity. (JF)