In view of the lack of reliable diagnostic parameters for predicting pregnancy-induced hypertension (PIH) the aim of this study was to test the prognostic value of electrophoretic urinary protein patterns. Based on experience with this method in nephrology, molecular weight related polyacrylamide-gel-electrophoresis (PAGE) of urinary proteins was used to distinguish between the different kinds of renal lesions (glomerular, tubular, combination, extrarenal). The analysis was carried out in two independent groups: urines of 126 non-selected pregnant women (1st group) were analysed at regular intervals. By chance, none of them had a history of previous PIH or hypertension, nor any signs of impaired renal function before or during the present pregnancy. In a 2nd group 124 women after severe PIH (pd greater than or equal to 110 mm Hg) were examined in part using PAGE, postpartum renal biopsy and long-term clinical follow up (greater than or equal to 1 year after PIH). In 29/124 cases data for all mentioned parameters was collected. 24 women of the prepartum group developed an electrophoretic pattern characteristic of glomerular proteinuria, which was persistent once found. PIH appeared greater than or equal to 8 weeks after the appearance of this pathological pattern in 15/24 women of this subgroup; 5 of 9 remaining women developed PIH in a subsequent pregnancy. None of the 102 women with other protein patterns developed PIH. In the 2nd group a close relationship was found between the glomerular protein patterns 0.5 to 3 years after PIH, clinical long-term follow up and renal biopsies about 1 year after PIH.(ABSTRACT TRUNCATED AT 250 WORDS)