Adverse effects of drug therapy on handwriting fluency attributed to increased attentional control have been observed in children with attention deficit hyperactivity disorder (ADHD). The writing performance of 8 children with ADHD was assessed using a digitizing tablet in a double-blind, placebo-controlled test. Participants wrote a phrase in cursive script both on and off stimulant medication writing normally, writing with eyes closed, and writing faster than normal. Medication reduced fluency of normal handwriting movements. When children with ADHD were instructed to write faster than normal or with eyes closed, however, more fluent and even automated movements resulted, even on medication. We also assessed 10 children with ADHD, 10 children without ADHD, 10 adults with ADHD, and 10 adults without ADHD. Participants with ADHD were assessed both on and off medication. Children with ADHD on medication were less fluent than children without ADHD. Without medication, Children with ADHD did not differ from children without ADHD; those on medication showed increased handwriting dysfluency. There was no significant difference between the adults. Both children and adults with ADHD could perform age-appropriate and automated handwriting movements. Children with ADHD on medication, however, gave more attention to the writing process, possibly hampering fluent handwriting movements.