Data from national entering first-grade populations of 1964 (N=12,225) and of 1972/1973 (N=4275/6653) show an 11-point increase in median raw score on the 102-item Metropolitan Readiness Tests. The increase is shown to be greater at the lower than at the higher ranges of the score scale, with the first quartile increasing by 13 points, the third quartile by 9. Gain in the median total score is spread unevenly over the six subtest areas, being greatest in Alphabet (recognizing lower-case letters by name) and least in Copying. In 1964 the first quartile on the Alphabet test was 5 letters, in 1972/1973 it was 12 letters. These changes in readiness development would seem to have significant implications for first-grade instruction. (Author)