To test the effects of calcium dobesilate (Doxium) in pregnancies complicated with pregnancy-induced hypertension or mild/moderate pre-eclampsia a double-blind, placebo-controlled pilot study was carried out. Primigravida patients (gestational age </=34 weeks) daily took 2 g Doxium or placebo until delivery. Twelve patients received placebo for 53 days, and 11 patients took the drug for 57 days on average. At the start of the study 2 patients in the placebo group (PG) and 8 in the Doxium group (DG) had pre-eclampsia. The mean arterial pressure (mean +/- SD) significantly decreased from 118 +/- 7 to 99 +/- 9 mm Hg in the DG (p = 0.003), while in the PG it had slightly increased by the end of the study. Proteinuria was higher in the DG at the start but not at the end; however, significant changes of this parameter were detected in neither of the groups throughout the study. Fibronectin decreased significantly in both groups but it was more pronounced in the DG (23.8 vs. 9.4%). Changes of platelet count, plasma and blood viscosity, and erythrocyte deformability were favourable in the DG but in the PG these parameters had deteriorated although the alterations were not significant. No marked differences were found between the two groups regarding fetal well-being, courses of deliveries, and the neonatal period. Neither maternal nor fetal/neonatal side effects were noticed. It seems that Doxium favourably influences the blood pressure and consequently decreases the requirement for medication and hospitalisation in cases of mild to moderate midtrimester hypertension.