This work presents a statistical analysis of the German version of the Wender Utah rating scale (WURS) for the retrospective diagnosis of attention-deficit/hyperactivity disorder (ADHD) in adults. Data were obtained from 703 subjects. Item selection according to item-total correlation scores, frequency, and plausibility led to a short version of the scale that includes 21 items with item-total correlations from 0.19 to 0.61. Retest reliability of the WURS-k was r=0.9.