In the spring of 1986, New York City began using the Metropolitan Achievement Test-6 (MAT-6) series to assess achievement in mathematics as part of a continuing end-of-year testing program. During the first two years of the program, appropriate levels of the shelf version of MAT-6 (Forms L and M) were administered to second through eighth graders. Since then, a customization process, described in this paper, has been undertaken due to concern expressed by teachers and district-level staff that the tests were not uniquely geared to assess the performance objectives specified in the New York City curriculum guides. For grades 2 through 8, approximately 200 new items were developed that clearly measured city curriculum objectives; approximately half of these items were taken from other tests that the MAT-6 publisher had available. The items were arranged on tryout sheets and piloted with student samples. The attempt to select tests that were perfect psychometric replicas of the shelf tests while also being perfect matches to the curriculum was not completely feasible. It also proved troublesome to determine difficulty levels for various items. Item selection is now completed, but equating techniques must be applied following the next spring's test administration. (TJH)