A procedure adequated to the study of forest potencial evaporation is presented. Meteorological datas were obtained by automatic weather stations installed on the tower's top, at level 45 m, and constitute part of a large whole of information, which come being formed in the scope of Micrometeorological Experiment, at Ducke Reserve near from Manaus-AM. Observational period was August/83 - April/85, and stations provided houvly measurements of wind velocity, air temperature and specific humidity, solar and net radiation.