We propose to develop and test a computer-based instrument for measuring the handwriting and drawing of children with attention deficit hyperactivity disorder (ADHD). The instrument consists of a digitizer which can continuously sample pen position and pen pressure as a subject writes on paper and a microcomputer for recording data from the digitizer. In Phase I we will measure the subjects' handwriting and drawing. The study is designed to establish feasibility, measure medication effects, and to compare the sensitivity of six parameters derived from the motoric data. We will test 20 children, ages 8 to 10 years, who have been diagnosed with ADHD and 20 normal controls matched in age and sex. Subjects will be tested when unmedicated and when medicated with their usual and standard dose of methylphenidate.