Thirty two women who were participating in an efficacy study comparing 10 mg ketorolac with 50 mg or 100 mg of pethidine in the relief of labour pain, underwent sampling of vein blood, for determination of plasma ketorolac concentrations. The sample was withdrawn at delivery and a sample of umbilical cord blood was withdrawn at the same time. The ratio of ketorolac concentrations in the cord blood sample: the maternal venous sample were calculated and plotted against the time elapsed between drug administration and sampling. Samples for one patient, withdrawn 24 min after dosing, had ketorolac concentrations below the quantification limit. The ratios in the remaining patients were all low and showed a tendency to increase with time. The mean ratio was 0.116 with a range of 0.04 in 2 patients, at 43 min and 1 h 6 min, to 0.25 at 6 h 34 min.