In recent years, increasing attention has been paid to teachers' classroom language as a variable in the formal learning process. The language used in class by teachers assumes additional importance in formal second language learning situations, where the target language as used by the teacher is not only the means for conveying content, but also a product of the underlying linguistic system to be acquired by the learners. The present paper reports on research which attempted to determine whether foreign language teachers' classroom speech is syntactically different from their speech among linguistic peers. The syntax of samples of the classroom language of eight TESOL teacher-trainees teaching adult English as a second language (ESL) courses was analyzed. Six measures of syntactic complexity were used. The subjects' classroom language was compared with samples of their speech among peers. In addition, the effect on syntactic complexity of two variables--the level of the classes and the times during the ten-week courses at which samples were collected--was examined. The data as measured by all six dependent variables indicate a process of syntactic simplification in the classroom language. Results suggest further that the degree of syntactic complexity was relatively stable over the ten-week period and that the syntactic complexity of the classroom speech varied as a function of the degree of proficiency the students were assumed to have. Implications of the findings for the formal second language learning process are discussed. (Author/AM)