We have investigated if pain intensity or analgesic requirements in hospital predicted pain intensity, pain duration or analgesic requirements at home in 611 children, aged 1-7 yr, after day-case adenoidectomy. We also investigated if ketoprofen 0.3-3.0 mg kg-1, administered pre-emptively i.v. during operation, modified pain at home. In hospital, a prospective, randomized, double-blind, placebo-controlled study design was performed. A standard anaesthetic technique was used in all children and fentanyl i.v. was available for rescue analgesia. After discharge, the study design was open, experimental, prospective and longitudinal. On return home, children were prescribed ketoprofen tablets 5 mg kg-1 day-1. Parents were asked to complete an analgesia diary; non-responders were contacted by telephone. The response rate was 91%. The number of doses of fentanyl given in hospital correlated with pain intensity at home (P < 0.001). There were no other correlations and no pre-emptive effect of ketoprofen.