Asperger syndrome (AS) is a pervasive developmental disorder recently introduced as a new diagnostic category in the ICD-10 and the DSM-IV. Along with motor clumsiness, pedantic speech has been proposed as a clinical feature of AS. However, few attempts have been made to define and measure this symptom. We studied 17 patients with AS (ICD-10; 14 male, 3 female; mean age 16.4 years, mean full-scale IQ 97) and compared them with a control group of 13 patients with normal-intelligence autism or high-functioning autism (HFA) (ICD-10/DSM-III-R; 12 male, 1 female; mean age 15.5 years, mean full-scale IQ 81.2). An operational definition of pedantic speech was formulated and a rating scale devised. 13 (76%) of the AS patients were rated as pedantic compared to 4 (31%) of the HFA group (chi 2 = 6.3; p = .01). Results suggest that pedantic speech is common in AS and may help differentiate AS from high-functioning autism.