['To determine whether there is a sex difference in placebo and ibuprofen analgesia expectancy.', 'We measured detection and tolerance thresholds for electrically induced pain in the ear lobe in healthy subjects (10 male, 10 female) to study sex differences in expectancy following either ibuprofen 800 mg or placebo in four different expectancy states. Subjects took ibuprofen or placebo in a two-by-two factorial design (the balanced placebo design). We randomly assigned subjects to start in one of the four expectancy states. We analysed the results using analysis of variance for repeated measures with baseline pain as a covariate.'] Are sex differences in analgesic response to ibuprofen influenced by expectancy : a randomized , crossover , balanced placebo-designed study?