Flow rate, pH, buffer capacity, viscosity, sialic acid, selected proteins (amylase, lysozyme, peroxidase, lactoferrin) and anions (thiocyanate, hypothiocyanite) were analysed in paraffin-stimulated whole saliva of 16 women during the three trimesters of pregnancy and post partum. Salivary pH and buffer capacity decreased towards late pregnancy, followed by a rapid and significant (p less than 0.01) increase after delivery. The specific activity of salivary peroxidase increased significantly (p less than 0.05) during the third trimester, thus supporting the concept of oestrogen-dependency of this enzyme. None of the other parameters changed significantly during pregnancy or lactation. The results suggest that the composition of human saliva is influenced by female sex steroids during pregnancy.