In mammals, the mechanisms regulating the initiation of follicle development remain poorly understood. We previously reported that testosterone induced the activation of porcine primordial follicles after 7 days of culture. Herein, the effect of KIT ligand (KL) on the viability, activation and development of porcine primordial follicles was examined. Ovarian strips containing primordial follicles were cultured for 7 days in a medium supplemented with KL (10, 100, 250 or 500 ng/ml). The percentage of degenerated follicles was significantly decreased (39 ± 2%) in the 100 ng/ml KL-treated group compared to the control (56 ± 1%), whereas almost all of the primordial follicles degenerated at higher concentrations of KL. No primordial follicles developed in culture at any concentration of KL. When ovarian strips were cultured in medium supplemented with testosterone (10^-6 M) KL (100 ng/ml), primordial follicles developed to early secondary follicles (5 ± 3%), however the total percentages of developing follicles in the testosterone group (21 ± 5%) and the testosterone KL group (28 ± 5%) were not significantly different. These results suggest that KL does not promote primordial follicle activation, although it does promote follicle viability in culture.