We have evaluated the biochemical and clinical parameters for early detection of their alterations in pregnant women with late preeclampsia. Eighty nine patients between 24 and 32 gestation weeks were studied. Fifteen of them (18%) developed arterial hypertension (mean 141.5 +/- 3mmHg). The perinatal results, gestational age at delivery, birth weight and Apgar score of the newborns were not significantly different among the groups that were evaluated. The microalbuminuria was analyzed through radioimmunoanalysis and reactive strips for the immunochemical semiquantitative determination. The calciura was analyzed using the compleximetric method and the urinary creatine using the colorimetric method of Jaffe. No significative differences were found among the results of each evaluated method. The RIA showed greater sensibility, greater specificity and greater positive or negative predictive value with respect to other methods, but the differences were not wide enough to consider it the method of choice. In the group of patients (n = 15) who developed arterial hypertension, all the biochemical methods showed a normality higher than 80%. We conclude that none of these methods used alone is useful for the early prediction of the appearance of preeclampsia.