BACKGROUND:Drug treatment forattention deficit disorder(ADD) was rare in the United Kingdom (UK) until in the mid-1990s. This contrasts with North America, where such treatment has been used to treat ADD for many decades. Since no quantitative data on theincidenceandprevalenceofdrug-treatedADD are available in theUK, we used the general practice research database (GPRD) to obtain such information.AIMS:To provide estimates ofincidenceandprevalenceof treated ADD in theUKfor the years 1996-2001.DESIGN OF STUDY:Follow-up study ofboysaged 5-14 years.SETTING:Data fromUKgeneral practices.METHODS:From the GPRD, we identified allboysaged 5-14 years who were prescribed methylphenidate for ADD. Based on the population in that age and sex category, we estimatedincidencerates and theprevalencefor treated ADD for the years 1996-2001.RESULTS:Theincidenceof first-time diagnosis of treated ADD increased amongboysfrom the age of 5 years to reach a peak inboysaged 9-10 years, after which theincidencerate decreased. No material change inincidencewas noted during the years 1996-2001. Theprevalenceof treated ADD was estimated to be 5.3 per 1000boysin 1999.CONCLUSION:Drug treatment for ADD forboystreated for thisdisorderin theUKis substantially lower than the proportion ofboystreated in North America.