Nowadays, quality has become a very important factor in almost all areas of endeavour. The data generated from tests for the assessment of potentially toxic chemicals is obviously no exception. It is necessary, therefore, that quality systems be developed to ensure that the data generated to support these tests are of good quality. An acceptable quality system should require that, where applicable, the tests be performed according to defined guidelines. Once defined guidelines have been identified for the type of test to be performed, it is then necessary to design a plan which describes how, when, where and by whom the data will be generated. If at all possible, the data should be generated according to written standard procedures which provide for the production of data to the same quality standard. The data should be generated and collected by properly trained staff using data collection systems (paper or electronic media) which ensure the accuracy, reliability and integrity of the data recorded. The data must then be recorded in such a way as to ensure that they are reported completely clearly and accurately. The report, whether it be in the form of scientific article, monograph or formal study report, should present the data in a consistent manner and allow for adequate reconstruction of the events which took place during the test. Finally, the report and the data supporting it should be verified to ensure that the test was carried out according to the relevant guidelines (if used), that the study plan was correctly followed and finally that all data were properly generated and accurately reported in the report.(ABSTRACT TRUNCATED AT 250 WORDS)