Using the standard indirect immunofluorescent (IIF) technique two types of autoantibodies are detected in the sera of patients with vasculitic disorders. These are cytoplasmic or classical antineutrophil cytoplasmic antibody (cANCA) and perinuclear anti-neutrophil cytoplasmic antibody (pANCA). In order to resolve the problems associated with the detection of pANCA an immunocytochemical technique-alkaline phosphatase anti-alkaline phosphatase (APAAP) was developed and used to detect ANCA in various groups of patients. Comparison with the standard immunofluorescence method showed that the results correlated only when immunostaining patterns were of the cANCA type. Detection of pANCA by APAAP was more uncertain than by immunofluorescence because of the greater number of staining patterns seen. Interference from antinuclear antibodies (ANA) appeared to cause more problems with the APAAP technique and sera containing ANA were not distinguished from pANCA using either immunofluorescence or APAAP. In conclusion, it appears that the APPAP technique is not a reliable method of the screening of ANCA and that pANCA has several antigenic specificities.