There is an often noted lack of research in the field of disorders of arithmetic skills. The present study assessed the prevalence in both an urban and a rural population sample of German schoolchildren, using standardized academic achievement tests. Eight school classes of third graders in each area were examined (n = 181,182; respectively). We found that 6.6 % (n = 12) of the rural and 6.59 % (n = 12) of the urban school children performed significantly worse in arithmetic than in their spelling tests. Since the diagnostic criteria for the Specific disorder of arithmetical skills and their significance are widely discussed, we attempted in a second step of the study to validate the diagnosis of the Specific disorder of arithmetical skills from a neuropsychological and medical viewpoint. For the validation we assessed clinical data, imaging and neurophysiologic studies as well as a neuropsychological test battery. Nine and five of the children, respectively, were available for this further evaluation. Although the majority of these probands (n = 10) had distinct arithmetic deficits, only three of them met the full diagnostic criteria of the ICD-10 for a Specific disorder of arithmetic skills. In a last step, we compared the data of both studies. Our data strongly support a thorough cliniconeurological, neuropsychological and academic assessment of students with a suspected Specific disorder of arithmetic skills. The current diagnostic criteria should be reconsidered and possibly modified towards a more psychopathologic definition. We stress the need that the condition becomes better known among all professions concerned with the care of children, as difficulties with acquiring arithmetic skills should be detected and approached appropriately as early as possible. The imperative demand of future empiric research is emphasized.