We followed 230 cases of phenylketonuria (PKU) from October 1984 to December 1994. Treatment was provided for 20 cases (8.7% of total) identified by neonatal screening programme, when the children were less than 3 months old. 48 cases (20.9%) were treated when the children were 3-12 months of age. 162 PKU children (70.4%) were diagnosed when they were already more than I year old. Urinary pterins of 116 patients and erythrocyte dihydropteridine reductase (DHPR) activity of 86 patients were determined. Tetrahydrobiopterin loading test was carried out on 3 cases. One patient was found to be DHPR deficient and another diagnosed as 6-pyruvoyl-tetrahydropterin synthase deficiency. The phenylalanine hydroxylase (PAH) gene in 65 patients were analyzed by PCR-ASO and PCR-SSCP. Novel PKU mutations not reported in the Western populations were identified. To reduce the cost of treatment, locally-made PKU diet was produced in 1991 after repeated clinical trials. Now more than 150 PKU patients are taking locally-made low ol free-phenylalanine (phe) diet which is supplemented with carnitine. The clinical results were satisfactory. Total and free carnitine blood levels in treated PKU subjects were significantly lower than those of controls (P < 0.01).