The bioavailability of commercial carbamazepine tablets with and without meals was compared to a propylene glycol solution with respect to extent of absorption in 6 normal humans after a dose of 6 mg/kg. The presence of dose-dependent kinetics within a clinically significant range was also investigated. Serum and urine samples were assayed by gas-liquid chromatography (GLC). Carbamazepine is rapidly absorbed from the propylene glycol solution. Eight per cent of the dose was absorbed from the commercial tablet, resulting in therapeutic serum concentrations (3 to 6 mcg/ml). The data were consistent with dissolution rate-limited absorption. Mean half-lives ranged from 31 to 35 hr. No dose-dependent kinetics were observed following administration of doses of 3, 6, or 9 mg/kg. The fraction of dose absorbed, the fraction excreted unchanged in urine, the time of maximum serum concentration, and absorption and elimination half-lives appear to be independent of dose. The time course of side effects could not be correlated with serum carbamazepine levels, suggesting that metabolites contributed to side effects.