The present experiments were designed to study male and female luteinizing hormone (LH) secretory patterns following pulsatile or continuous LH-releasing hormone (LHRH) administration using a perifused dispersed rat anterior pituitary cell culture system. In male cells, consistent LH responses were elicited by hourly LHRH pulses (30 pmol), whereas in the female cells (proestrus or diestrus I), a statistically significant (P less than or equal to 0.01) decrease in the LH secretion occurred with successive LHRH pulses. Proestrous cells secreted significantly (P less than or equal to 0.01) more LH than diestrous cells during the first 24 h but not after 48 h in culture. When exposed to a 6-h continuous infusion of LHRH (10 nM), male cells released LH in a single phase and female cells secreted LH in a biphasic pattern. These data suggest that significant sex differences exist in the rat LH secretory pattern elicited by LHRH in vitro.