After a drastic mathematics curriculum change in The Netherlands in 1993, a study on the alignment of intended, implemented, and attained curriculum was carried out using TIMSS-99. For benchmarking, identical instruments were used in a neighboring country (Flanders), and for science. Two innovative methodological features were: (1) the teachers' judgments on concrete items through an item-based instrument, and (2) the use of the partial overlap of the TIMSS test and the Dutch intended mathematics curriculum. Comparing the results, the mathematics curricular alignment in The Netherlands had reached an acceptable level, 6 years after 1993.