In mammals leptin plays a key role in regulating the whole-body energy homeostasis and is important for for normal reproduction Much evidence indicates that leptin mediates the undernutrition-induced alterations of the reproductive axis (Ahima and Flier, 2000). In birds leptin gene was cloned in chickens (Taouis et al., 1998) and recombinant chicken leptin (chLep) was prepared in our laboratory (Raver et al., 1998). Unlike mammals, leptin is expressed not only in the adipose tissue but also in liver and leptin plasma level is lower in fasted than in fed hens (Dridi et al., 2000). However, the importance of leptin in avian reproduction is not known. Therefore, the aim of the present study was to examine whether in chickens leptin affects events occuring in the ovary during fasting.