The immediate effects of methylphenidate on cognitive attention in 15 children (13 males, 2 females; mean age 9y 5m) with attention deficit hyperactivity disorder (ADHD) were assessed at Guy's Hospital, Great Ormond Street Children's Hospital, and Institute of Child Health, University College, London. All subjects were of average intelligence, but they demonstrated significant impairments in cognitive attention, especially sustained attention, at base-line, in comparison with a control group. Significant improvements in attention were measured in the ADHD children compared to untreated controls, when retested on the same day and after receiving methylphenidate in a single 10 mg dose. 
COMMENT. Is the cognitive improvement following a single dose of methylphenidate (MPH) predictive of a beneficial long-term response? The clinical judgment of severity of ADHD and improvement in Conners Rating Scales after a single dose of MPH (10 mg) were predictive of cross-situational improvement after 4 weeks of MPH treatment (Ped Neur Briefs Aug 1995) . High IQ, young age, and low rates of comorbid anxiety were additional predictors of a long-term response.
The acute effects of MPH in 3 dosages (0.3, 0.6, and 0.9 mg/kg) on the performance of 17 ADHD children included increased cognitive flexibility and improved persistence (Ped Neur Briefs July 1995) . Doses of 0.3 to 0.6 mg/kg were recommended in clinical practice, larger doses having little advantage and causing possible impairment of cognitive functioning with multiple daily doses.