THIS INVESTIGATION WAS DESIGNED TO ASSESS THE INFLUENCE OF AGE OF ENTRANCE INTO THE FIRST GRADE ON ARITHMETIC ACHIEVEMENT. THE SCORES ON ARITHMETIC ACHIEVEMENT TESTS WERE COMPARED FOR 378 LATE AND EARLY ENTRANT BOYS AND GIRLS IN THE FIRST TO SIXTH GRADES. THE LATE ENTRANTS WERE BETWEEN 8 AND 9 MONTHS OLDER THAN THE EARLY ENTRANTS. THEORETICALLY, AN EARLY START SHOULD NOT RESULT IN SIGNIFICANT GAINS OF LONG TERM DURATION. IN TESTING THIS CONCLUSION, THE ARITHMETIC ACHIEVEMENT SCORES WERE COMPARED ON THE BASIS OF BOTH GRADE AND AGE. FOR BOTH BOYS AND GIRLS, THE RESULTS SHOWED THAT, MEASURED ON THE BASIS OF GRADE, THE ARITHMETIC ACHIEVEMENT SCORES WERE HIGHER FOR THE LATE ENTRANTS, BUT, MEASURED ON THE BASIS OF EQUATED AGE, THE EARLY ENTRANTS SCORED HIGHER. THESE RESULTS SUPPORT OTHER FINDINGS IN THE AREA AND LEAD TO THE CONCLUSIONS THAT (1) PUPILS IN THE AMERICAN GRADE SCHOOLS CAN LEARN EARLIER IN LIFE THAN NOW THOUGHT, (2) THEY CAN LEARN MORE COMPLEX ARITHMETIC, AND (3) SUCH LEARNING MAY HAVE AN ENDURING CUMULATIVE EFFECT AT AGE 11. PERHAPS, AS A SUGGESTION, THE PRESENT ARITHMETIC CURRICULUM SHOULD BE REEVALUATED, FOR IT HAS TOO FREQUENTLY BEEN FOUND INSUFFICIENTLY STIMULATING TO THE PUPILS. THIS PAPER WAS PRESENTED TO THE AMERICAN EDUCATIONAL RESEARCH ASSOCIATION, (CHICAGO, FEBRUARY 7, 1968). (WD)