The course of 41 pregnancies was studied in 25 patients with renal disease. Histological classification of the disease in each patient was made by renal biopsy. The analysis suggests that the course of pregnancy in women with coexistent renal disease correlates with the underlying renal lesion and probably with the glomerular filtration rate and blood pressure. In patients with heavy proteinuria there is increased oedema formation, making the nephrotic syndrome a frequent complication.