The effects on Cone Penetration Resistance caused by four tillage implements (chisel plow, disk plough, disk harrow and rotatiller) were assesed on an Andisol, using a digital penetrometer. The results showed the treatments using rota-tiller and those using disk plough and disk harrow caused the maximun soilloosening. However those treatments were the most sensitive to compaction due to the traffic of tractor wheels. This work did not present conclusive evidence that bottom of furrow made by disk plough is a place of high risk for subsoil cornpactlon. Cone penetration resistance looks like a good index to assess changes in physical properties of the soil caused by tillage operations and machinery traffic.