Glomerular IgA deposits in patients with celiac disease. Glomerular immunopathology was studied in 25 patients with newly diagnosed celiac disease. None had clinical signs of renal disease. Glomeruli were obtained by fine-needle aspiration biopsy. The specimens were processed and studied by indirect immunofluorescence for immunoglobulins and complement. Mesangial IgA was found in 8 of the patients. It occurred occasionally together with slight IgG or IgM, but C3 was not seen in these patients. IgA-class circulating immune complexes (CIC), antireticulin antibodies (ARA), antigliadin antibodies (AGA), and rheumatoid factor (RF) occurred significantly more often in the patients with mesangial IgA than in the 17 patients having no mesangial IgA. The patients with mesangial IgA also had significantly higher mean levels of serum IgA, IgA-ARA and IgA-AGA than those without. The results suggest that glomerular mesangial deposits of IgA occur frequently in untreated celiac disease and that they are in some way associated with circulating IgA-class antibodies and immune complexes. In this situation IgA seems to be deposited without being able to induce clinically overt glomerulonephritis, a circumstance that may be related to the lack of complement in the deposits. 