A language evaluation instrument was devised to assess the accuracy of program implementation by teachers of four Australian preschool programs. The Teacher Language Instrument (TLI) categorizes each verbal episode of a teaching interchange for both mode and function. Five general mode categories of teacher language behavior--statements, questions, imperatives, reinforcers, and facilitators--were differentiated. Similarly, five general categories of function--regulatory, heuristic, social, administrative and resource--were developed. Evaluation data were collected on videotape and the classroom events were sampled using a combination of event- and time- sampling procedures. Except for ad hoc recording of all especially significant events, samples of teacher speech were recorded every 15 minutes. The verbal interactions of all four teachers at each school studied were recorded in 10 minute segments. It was found that the four programs were implemented along intended guidelines. Among the results, teachers in the Cognitive and Competency Programs used the questioning mode more frequently than the stating mode, while for the Behaviorist and Contemporary Programs the opposite order occurred. Across all four programs the functions occurred in descending order as follows: regulatory, heuristic, social, resource and administrative. Definitions of mode and function categories, as well as tables depicting percentage of observations by language category and site, are appended. (Author/RH)