Objective: A phenylalanine-restricted diet is the mainstay of phenylketonuria (PKU) treatment but does not normally provide enough protein for growth requirements. We evaluated the effect of a phenylalanine-restricted diet on growth parameters of Egyptian children with PKU.Methods: Twenty-eight PKU children were evaluated for weight, height, and body mass index (BMI) and were compared with matched controls at baseline and then their baseline parameters were compared with those collected 2 years later.Results: At baseline, 86% of PKU children were normal weight and 11% below; and 75% were in the normal height percentile and 25% below. For BMI, 68% were normal, 21% overweight and 11% obese. Two years later, all PKU children were in the normal weight percentile, and 79% were in the normal height percentile and 21% below. For BMI, 46% were normal, 36% overweight and 18% obese. For PKU children below normal percentile at baseline, normal weight, but not height, was reached after 2 years. Also, more PKU children became overweight or obese after 2 years. Conclusions:Early detection of PKU and early use of a phenylalanine-restricted diet may avoid growth retardation of height, but care should be taken to avoid patients becoming overweight or obese over time.