Reversed circulation drilling is a fast and cheap method. Unfortunately, the samples obtained provide no much information on mineralogy and the metal content can be no very reliable. Since the sample are not very deeper, information and data have to analyzed and studied carefully. A hammer transmitting its force through drill rods to a rotating drill bit which does the penetration. Air or water is circulated through the drill rods to cool the bit and carry out the rock cuttings to the collar of the hole, where they are collected and prepared for study and assay. The method works well where the wall rock is competent, dry and impermeable. It has a practical depth limit of 45 to 90 m. Metal values may be lost by seepage into the wall rock, or added or diluted by caving or seepage into the drill hole. Reverse circulation of the drill water down the hole and up the drill rods greatly improves the accuracy of the sample. Sometime, mining companies during the first months of operation employ this method to study zones that were not studied well during the exploration program. Results are different. For example, by employing a core drilling program the average gold content was 5 g/t. however, the second method on the same place gave higher values, 10 g/t. This situation creates doubt and conflict between the design criteria and the new values. For this reason, results obtained by reversed circulation need a special study and interpretation.