Kindling is a very suitable animal model for studying basis mechanisms of epilepsy. In this model , repeated exposure to weak electrical or chemical increases neuronal excitability and there fore decreases the threshold for induction of epileptic seizures. According to abundant distribution of opioid peptides and their receptors in different brain structures and also the role of these receptors on the excitability of neurons,we studies the effects of repeated morphine administration on the induction and modulation of epileptic seizures. Male rats were made dependent by gradual increase in concentration s of morphine sulphate in drinking water. Then, pentylenetetrazole ( PTZ,30 mg\ kg) was injected intraperitoneally at 48 hours interval and epileptic seizures of control and dependent rats were compared in 22 serial injection s. In another series of experiment, morphine _ dependence was induced after kindling and 20 days later, seizures response s to a single subtreshold dose of PTZ were compared. The results showed that morphine dependence, facilitate s the induction of chemical kindling, but when kindling is induced , morphine _ dependence has no effect on it. It seems that morphine _ dependence has important effects on the neuronal excitability that is presented as facilities of kindling induction in this study.