Atlantic cod is potentially an important species for fish farming. One obstacle today is early sexual maturation in captivity. Detailed knowledge of the mechanisms involved in cod maturation is essential for solving this problem. We therefore intend to characterize the gonadotropin releasing hormone (GnRH) system in cod. As a first step, we have obtained preliminary data on basic electrophysiological properties of cod pituitary cells. Primary cultures of pituitary cells from Atlantic cod were prepared by trypsin treatment and mechanical dispersion. Electrophysiological recordings were performed using the perforated patch clamp method. Gonadotropes in goldfish are the largest of the pituitary cell types. Large cells were therefore selected for recordings. Spontaneous action potentials (APs) were observed in about 30% of the cells. The APs display both a fast Na+ component and a prolonged Ca²⁺ plateau. Correspondingly, the inward current elicited by depolarizing steps consists of both a transient, tetrodotoxin-sensitive component (at 0 mV: -130 ± 50 pA, n = 5) and a nifedipine-sensitive component that was sustained when Ba²⁺ was the main current carrier (at 0 mV: -17.7 ± 6.2 pA, n = 3). The outward current was partially blocked by 5 mM tetraethylammonium (reduction to 40.7 ± 8.4%, n = 6) and 10 mM 4-aminopyridin (reduction of early activated current to 43.8 ± 5.2% (n = 10). We conclude that large pituitary cells from Atlantic cod display electrophysiological properties necessary for controlling hormone secretion via APs and Ca²⁺ influx. Characterization of the electrophysiological response to GnRH in identified gonadotropes will be performed in future experiments.