1. Two national surveys were conducted (in 1972 and 1980) to ensure that the register was complete. From the mid 1960s onwards a national programme of routine screening of urine for phenylketonuria between 3 and 6 weeks of age was progressively replaced by a system of blood testing between the 6th and 14th days'4; the change was virtually complete by 1971. For this reason we have distinguished between children born from 1964 to 1971 (cohort 1) and those born from 1972 to 1980 (cohort,2).
2. Evaluation of treatment begun in the first three months of life in 184 cases of phenylketonuria;Hudson, F.P.; Mordaunt, V.L.; Leahy, I.;Arch Dis C>hild,1970
3. Intellectual phenylalanine concentrations have reported mean IQs that are closer to our revised IQ assessment of 111 four year old children with phenylketonuris;Dobson, J.C.; Williamson, M.L.; Azen, C.; Koch, R.;Pediatrics
4. Intelligence and school performance in early treated classical phenylketonuria patients. The French Collaborative Study;Saudubray, J.M.; Rey, F.; Ogier, H.;Eur J Pediatr,1987
5. Behaviour disturbance in eight year old children with early trea;i, Smith; M, Beasley; OH, Wolff; EA, Ades,1988