Freshly isolated bovine non-pigmented ciliary epithelial cells were studied using the whole-cell voltage-clamp and permeabilized patch techniques. In a study of 148 cells three classes of cell were found; those containing inward currents alone, 31%; those containing outward currents alone, 37% and those containing both inward and outward currents, 32%.The outward currents exhibited slow, delayed activation, were blocked by tetraethylammonium (TEA+) but were not effected by changes in [Cai] suggesting they are K+-currents similar to IK(V), the delayed rectifier. The inward currents were reduced by TEA+and blocked by Cs+suggesting they are inward rectifier K+-currents.Intracellular cAMP levels were increased by isoprenaline with a Kaof 20nM. However, the resting membrane potential recorded from whole ciliary processes in intracellular microeletrode studies was not effected by adrenergic stimulation, neither were the leak current, the outward current nor the sustained inward current significantly effected by isoprenaline, noradrenaline or dibutyryl-cAMP in whole-cell and permeabilized patch clamp studies.