The frequency of antinuclear antibodies (ANA) and rheumatoid factor (RF) was investigated in 118 apparently healthy children (56 male, 62 female). The mean age was 9.8+/-2.3 years. Antinuclear antibodies (ANA) were detected by indirect immunofluorescence, using a Hep-2 cell substrate. Nephelometry was used to quantify RF in 116 children. Five serum samples (4%, 3M, 2F) were ANA-positive in low titers and all had a speckled pattern. None of the ANA-positive children had other extractable antinuclear antibodies. Rheumatoid factor (RF) was over 25 IU/ml in tour children (3%, 3F, 1M), None of these was positive for both antibodies.