Objectives ‐ Our aim was to investigate the diagnostic impact of skin biopsies in CADASIL patients. Materials and methods ‐ Eight consenting CADASIL patients belonging to a German‐Caucasian kindred were assessed clinically, genetically, by MRI and skin biopsy. Skin biopsy results were compared to 5 patients suffering from sporadic leucoencephalopathies (control group). Results ‐ Six CADASIL patients presented with symptoms ranging from migraine to severe tetraparesis with dementia. Two clinically unaffected patients had abnormal MRIs. On MRI 7 patients showed various degrees of leucoencephalopathy. One 22‐year‐old woman with migraine had a normal MRI. Granular, electron dense, osmiophilic material (GEM) was found in skin biopsies of all 8 patients including the 22‐year‐old woman with migraine and a normal MRI. As shown by genetic linkage analysis she was carrying the disease haplotype. GEM was not found in the control group. Conclusion ‐ Our findings substantiate the impact of skin biopsies in defining the carrier status in CADASIL families.