The effects of adrenergic drugs on intracellular electrical potential difference (PD) of rabbit ciliary epithelial cells were investigated. Epinephrine as well as norepinephrine hyperpolar-ized the PD at lower concentrations (10−6M) and depolarized the PD at higher concentrations (>10−5M). Isoproterenol produced a depolarization of PDIand phenylephrine caused a hyperpolar-ization only. After pretreatment with propranolol, the change of PDIby isoproterenol was minimal. Selective agonists and antagonists were used to further characterize adrenergic effects on the PDI. Both beta1, and beta2agonists caused a depolarization of PDIwhile both beta2. and beta2antagonists produced a hyperpolarization. Alpha1, antagonist depolarized the PDIand alpha2antagonist hyperpolarized the PDI. Such electrophysiological effects of the adrenergic drugs confirm the presence of alpha and beta adrenoceptors in the rabbit ciliary epithelial cells.