Certification of major components of x-ray equipment by the Bureau of Radiological Health of the Food and Drug Administration has created a renewed interest in the performance of diagnostic x-ray systems. Although the certification performance criteria, major component specification data, and assembly data is submitted by the manufacturers to the Bureau of Radiological Health; assembly and calibration of the diagnostic x-ray system depends on the assembler. Even though x-ray system components exhibit certification labels, there is no guarantee that the systems meet the compliance standards. In addition to the manufacturers' specifications and HEW requirements, we have developed supplemental performance specifications. Acceptance testing of diagnostic x-ray equipment prior to final payment has been used to check that the manufacturers meet the criteria established by BRH; to check the calibration of the various x-ray systems (generator/tube, collimator, automatic exposure control, etc.); and to develop supplementary testing criteria. The performance criteria, specifications, and equipment acceptance tests, including before and after measurements for several units, will be discussed. The results will demonstrate that our desired specifications can be achieved.