Thirteen healthy volunteers received 1 mg of alprazolam, as the commercially available oral tablet, by sublingual and oral routes on two occasions in random sequence. Plasma alprazolam concentrations during 48 hours after each dose were measured by electron-capture gas-liquid chromatography. The peak plasma concentration after sublingual dosage was higher than after oral administration (17.3 vs. 14.9 ng/ml), and the time of peak concentration following sublingual administration was reached (1.17 vs. 1.73 hours after dose). However, these differences did not reach statistical significance. The mean total area under the plasma concentration curve for sublingual administration was slightly but not significantly larger than that following oral dosage (203.7 vs. 194.4 hr.ng/ml) and no significant differences between sublingual and oral dosage were found for elimination half-life (11.7 vs. 11.8 hours) or for clearance (86.4 vs. 92.4 ml/min). Thus, alprazolam absorption following sublingual administration is as rapid as after oral dosage on an empty stomach, and completeness of absorption is comparable. In clinical terms, sublingual and oral dosages of alprazolam are likely to be therapeutically equivalent. The sublingual route may be a useful alternative for panic disorder patients who cannot swallow pills or for those who do not have access to a liquid at the time of dosing.