In the present study, plasma oxytocin and prostaglandin F2 alpha metabolite (PGFM) concentrations were measured in 46 patients admitted for preterm labour. Gestational age ranged from 20-34 weeks. Samples were collected 12 hours before and after initiation of tocolysis. Patients with a premature rupture of the membranes and/or intra-amniotic infection were excluded in this study. There was a significant difference in the oxytocin (p = 0.05) and PGFM levels (p = 0.007, after 12 hours: p = 0.004) between a control group without preterm labour and women with preterm labour. No differences were seen between the successfully treated (delivery more than 5 days after start of tocolysis) and the failure group. There was no significantly different increase or decrease in PGFM and Oxytocin plasma levels between treatment failures and successfully treated patients.