A great number of studies on women as well as experiments on animals support the association of silent intrauterine infection with the initiation of preterm labour. However, the success of antibiotic therapy in reducing bacteria-induced labour in animals could only be confirmed in few reports concerning women in preterm labour. Disregarding direct effects of bacterial products such as Phospholipase-A2 and endotoxins evidence suggests that immunological effects (release of Cytokines) may enhance the synthesis of prostaglandins in the uterus, placenta and fetal membranes. New therapeutical approaches are in discussion, but only time will tell whether a reduced rate of women with failed tocolysis will be the result.