The authors evaluated the course and prognosis of the disease in 109 children with minor glomerular abnormalities manifested clinically in 45.9% as nephrotic syndrome (NS), in 33% as nephritic syndrome (GN), in 11.9% as isolated haematuria (IH) and in 9.2% as Schönlein-Henoch's purpura (PSH). In NS 78% of the children had before biopsy of the kidneys frequent relapses, 22% were resistant to cortisonoids. After biopsy all children were given cortisonoids, 94% immunosuppressive treatment with cytostatics and some of the children additional treatment. The number of resistant cases declined to 10% and the mean number of relapses from four to one in 12 months. Children under five years had more relapses (P less than 0.05) but also more complete remissions (P less than 0.001) than older children. Relapses occurred up to 10.2 years after the onset of the disease (mean = 4 years). With advancing age and duration of the disease their number declined after treatment. An adverse symptom was resistance to cortisonoids and immunosuppressive treatment, major haematuria and persisting hypertension but not immunological activity (elevated level of immune complexes, reduced C3, positive immunohistochemical finding in renal tissue). The morphological finding which at the onset was slightly beyond the range of minor abnormalities had a poorer prognosis when associated with greater clinical activity. The group developed 88% complete remissions and 6% CHRI. After 22 years the probability of survival in complete continual remission is 66%, the probability in CHRI is 10% (with morphological progression). In nephritic syndrome the children were given after biopsy prednisone in 80.6% and cytostatics in 44.4%. In PSH this treatment was given to 100% and 60% of the children, in IH to 61.5% and 7.7%. On evaluation in nephritic syndrome complete remission was recorded in 47.2%, after 0.4-10.5 years since the onset of the disease; 30.6% did not improve and in 2.8% CHRI developed. In PSH remission developed in 60% after 0.8-6.9 years, no improvement was recorded in 20%, incl. 10% where CHRI developed after a resistant course of NS. In IH 84.6% of the patients did not improve, but in none the renal function deteriorated. The course was in all instances milder than in NS, most frequently only with microscopic haematuria and/or slight proteinuria, respectively minor immunological activity. In the entire group of minor glomerular abnormalities complete remission was achieved in two-thirds of the children, in one quarter the disease did not improve, incl. 4.6% where CHRI developed, always associated with progression of morphological changes.(ABSTRACT TRUNCATED AT 400 WORDS)