To define the diagnostic meaning of antineutrophil cytoplasmic antibodies (ANCA) positivity in children, we analysed 1485 consecutive sera sent for routine immunological investigation to our department from January to August 1996. Using this large screening, we identified the most typical clinical disorders associated with ANCA in childhood. Out of 1485 indirect immunofluorescence (IIF) tests for ANCA, 143 were ANCA positive, 70 had a cytoplasmic IIF pattern (c-ANCA), and 73 a perinuclear IIF pattern (p-ANCA). The ANCA associated diseases in childhood were cystic fibrosis (CF) (31 c-ANCA, 7 p-ANCA positive out of 71 CF children investigated), juvenile chronic arthritis (JCA) (21 p-ANCA positive out of 78), auto-immune hepatitis (AIH) (4 c-ANCA and 12 p-ANCA positive out of 19), and ulcerative colitis (UC) (2 c-ANCA, 5 p-ANCA positive out of 15). In cases of c-ANCA positivity we determined the antigenic specificity of ANCA for proteinase 3 and/or bactericidal/permeability increasing protein. Borderline anti-proteinase 3 levels were found in CF, and in high levels in one boy with Wegener granulomatosis. Bactericidal/permeability increasing protein was characteristic target antigen in children with CF. p-ANCA positive children were further tested for the specificity for myeloperoxidase, which was detected mostly in children with JCA.The spectrum of diseases associated with ANCA in children includes, besides the diagnostic associations typical for adults, several typical pediatric entities, mainly juvenile chronic arthritis and cystic fibrosis.