We have studied the effects of age and sex on the pharmacokinetics and the systemic availability of transnasal butorphanol in a randomized, two-way, crossover study of 48 subjects: young men and women, and elderly men and women. Each subject took a single 1 mg dose of intravenous and transnasal butorphanol tartrate on separate occasions with a one-week washout period. Blood samples were collected over 16 hours. Plasma butorphanol concentrations were determined using radioimmunoassay. The AUC of plasma butorphanol concentrations after an intravenous injection were higher in the elderly women than in the other groups. However, there were no significant differences in Cmax and AUC between the groups after transnasal administration. The mean systemic availability of transnasal butorphanol was about 70 %, except for the elderly women (48 %). After intravenous and transnasal administration, the half-life and mean residence time were greater in the elderly than the young. Clearance was lower in women than men. Apparent volume of distribution was higher for elderly men than the others. The age- and sex-related changes in the pharmacokinetics of transnasal butorphanol are not large enough to necessitate dosage differences.