The effect of an ascending dose regimen on the development of tolerance to diazepam's anticonvulsant effect was assessed. During the 22 trials of the tolerance development phase, amygdala-kindled rats received either a series of dosage injections ranging from high (10 mg/kg), to low (1.0 mg/kg), and ascending (1.0 mg/kg and increased by 0.2-mg/kg increments to 3.0 mg/kg) or saline injections. Diazepam was administered by ip injection once every 48 hr, and each injection was followed 1 hr later by a convulsive stimulation. The ascending dose rats displayed significantly more tolerance to the anticonvulsant effect of diazepam than did the high dose, low dose, or saline rats. By contrast, both the ascending and high dose rats displayed a significant withdrawal effect (i.e., increased duration of convulsions) after the cessation of diazepam injections. Results demonstrate that administration of ascending dosages can facilitate the development of tolerance to anticonvulsant drug effects and that tolerance and withdrawal are not necessarily inextricably related.