One of the key tasks for the persons in charge of a neonatal screening laboratory is the control and maintenance of the quality of analytical results. The process of examining every day hundreds of blood spot samples obtained from newborn babies in order to divide the population of neonates into a low risk group and a high risk group, presents several challenges with respect to organisation, analytical accuracy and precision and effectiveness in the recall and treatment procedures. Quality in neonatal screening is not determined solely by the analytical performance of the laboratory; all the steps of the neonatal screening "system” contribute to the overall quality and performance. Conclusion: programmes for the monitoring of the quality of neonatal screening have to be multidisciplinary and not restricted to the laboratory alone; not only analytical performance, but also the procedures used throughout the programme have to be monitore