This was an exploratory study to examine the use of atypical antipsychotics in an attention-deficit/hyperactivity disorder (ADHD) clinic. A total of 194 patients was examined to compare those receiving atypical or second-generation antipsychotics (atypicals) from those who were not. A sample of 27 children on atypicals received laboratory investigation for indicators of possible metabolic effects. In all, 19.1% of the patients in the clinic were receiving atypicals with a mean duration of 313 days; 36 of 37 patients on atypicals had received risperidone, with a mean dose of 0.62 mg. Children receiving atypicals were statistically more likely to have a severe co-morbid disorder, a lower Children's Global Assessment Scale score, a greater total score on the teacher Strengths and Difficulties Questionnaire, and greater difficulty with parent-rated symptoms of being touchy, worried, rages, and explosive outbursts. There were no differences found in measures of functioning, adaptive skills, quality of life, or ADHD symptoms. In the subset of children studied for potential metabolic effects, 68.0% had a waist circumference > or =90(th) percentile that was independent of weight gain, 18.5% had impaired fasting glucose, 12.5% had elevated blood pressure, 11.1% had elevated triglycerides, and 16.7% met full criteria for metabolic syndrome. Clinical implementation of the efficacy studies of risperidone for disruptive behavior disorders has led to a significant change in practice. Almost 1 in 5 patients are now receiving atypical neuroleptics, typically to treat severe co-morbid disorders and symptoms other than ADHD per se. Despite these children receiving low doses, concomitant stimulants, and low body mass index z-scores, a significant proportion of children demonstrated either one or more components or the full criteria for metabolic syndrome.