The Ventós-Castellar aquifer is a small karstic system located in the province of Alicante (Spain). An exhaustive monitoring is being acomplished on this aquifer to quantify its natural recharge. The study of the piezometric data shows the great influence that exercise the climatic factors in the aquifers with areas of recharge of small extension. The analysis ofthe pluviomectric data and the drop ot the water leve has allowed to establish that those rainfalls above 7 7 mm reach the saturated zone and become effective rainfalls. During the last years we have analyzed 2 events of recharge; theirs infiltration rates have been between 5 and 8% of the total measured rain