AN INSTRUMENT FOR MEASURING LANGUAGE MATURITY SHOULD BE EASILY ADMINISTRABLE AND SCOREABLE AND SHOULD BE BASED ON VALID INDICES OF LANGUAGE MATURITY. A RECENT STUDY BY KELLOG W. HUNT SUGGESTED THAT THESE INDICES BE BASED ON A NEW SYNTACTIC UNIT, THE T-UNIT, CONSISTING OF 1 MAIN CLAUSE TOGETHER WITH ANY CLAUSES SUBORDINATED TO IT. COORDINATED MAIN CLAUSES, WHICH ARE USUALLY A SIGN OF IMMATURITY, WILL THUS HAVE NO EFFECT ON THE INDEX. HUNT'S STUDIES, BASED ON 1000-WORD SAMPLES, INDICATED THAT T-UNIT LENGTH, CLAUSE LENGTH, AND NUMBER OF CLAUSES PER T-UNIT INCREASED FROM GRADES 4 TO 12. TO SEE IF THE INDICES COULD BE RELIABLY COMPUTED FROM SHORTER SAMPLES, 80 CHILDREN IN GRADES 4, 6, AND 8 WERE ASKED TO REWRITE A NARRATIVE COMPOSED OF SIMPLE DECLARATIVE SENTENCES, COMBINING THESE INTO LONGER UNITS. ALSO, 69 CHILDREN IN GRADES 4, 8, AND 12 WERE ASKED TO REWRITE A STRUCTURALLY SIMPLIFIED EXPOSITORY ESSAY USING LONGER SENTENCES. OBSERVED INCREASES WITH GRADE IN THE CLAUSE LENGTH, T-UNIT LENGTH, AND NUMBER OF CLAUSES PER T-UNIT WERE STATISTICALLY SIGNIFICANT. BECAUSE OF THE INTERRELATION OF THE INDICES, T-UNIT LENGTH APPEARS TO BE THE MOST USEFUL INDEX. FURTHER REFINEMENT OF THE NARRATIVE AND THE ESSAY IS NECESSARY, TOGETHER WITH STUDIES TO DETERMINE THEIR GENERAL VALIDITY AND RELIABILITY. THE PAPER WAS PRESENTED AT THE ANNUAL MEETING OF AMERICAN EDUCATIONAL RESEARCH ASSOCIATION, FEBRUARY 9, 1968. (DR)