Phenylketonruia (PKU) is an inherited metabolic disorder that results in progressive mental retardation. PKU is a paradigm of a disease that can be identified by proper screening of newborns and medical follow-up in order to prevent serious complications. The present study was designed to evaluate the Palestinian national screening programme for PKU in the Gaza Strip. Data about the screening of PKU in the Gaza Strip were obtained from the records of the healthcare centers of the Palestinian Ministry of Health (MOH) during the year 2000. In addition, PKU patients and families were interviewed. The results showed that the prevalence of PKU in the Gaza Strip varied considerably between the different regions with an overall prevalence of 6.35/100,000, while the maximum prevalence of 28.3/100,000 occurred in the rural areas. Coverage of PKU testing in the Gaza Strip is limited to about 35.3 per cent of the total newborns, who are delivered and receive health care at the government clinics. Among those newborns delivered at the government clinics, the percentage of PKU screening is about 87.8 per cent. However, PKU testing is not carried out at UNRWA clinics where about two-thirds of newborn deliveries take place. On average, 61 per cent of PKU testing is made in the infant's second week, ranging between 11 and 17 days, and the remaining (39 per cent) are tested thereafter. Approximately 60 per cent of PKU patients had consanguine parents (first cousins), while 7.7 per cent had no consanguinity. Only 43.1 per cent of PKU patients were fed on the specialized low phenylalanine milk. An inverse correlation was reported between the use of low phenylalanine milk and age. A total of 35.4 per cent of the PKU patients were regularly monitored by blood tests each month, 47.7 per cent had not been tested for the previous year. It was concluded that the PKU screening programme has to be improved, the screening methods should be reviewed, and the screening coverage should include all the newborns in the Gaza Strip.