The leaf life-span was studied for twenty-one species of ferns in the Kii Peninsula, southern Japan. Each leaf was marked and monitored during the period from early emergence to the final stage of decaying. Field investigations were carried out at monthly intervals from April, 1989,to December, 1992. Generally, the fern leaves were not defoliated and the degree of decaying was shown by the green area present (percentage to the total laminal area). There were two types of decaying in evergreen species -sudden and gradual decaying. In both types, the decaying of old leaves was accelerated just in the period of emergence of new leaves. Leaf life-spans of most summer green species were about 200 days. Of the ferns examined, Asplenium wrightii had the longest (1117 days) mean leaf life-span.