Abstract. As saliva is an easily accessible biological material, compared with 24‐hour urine and blood, the salivary concentration of estriol was studied from the 30th to the 41st week of gestation in 268 samples from 124 normal pregnancies. At the same time, venous blood samples were drawn and analyzed for total and unconjugated estriol. The mean values for the concentration of total estriol in saliva in the 30th and 41st weeks were 2.8 and 7.2 nmol/l respectively. The salivary estriol concentration appears to increase in perfect conformity with its serum concentration in the course of gestation. If estriol in saliva also reflects low serum values and an impaired function of the feto‐placental unit, analyses of the saliva may be applicable as a screening procedure in high‐risk pregnancies.