This paper presents some principles and bases which are worth considera-tion in the selection of analytical elements for samples collected in1:50,000geochemical reconnaissance, and, for reader's reference, gives examples about theselection of indicator elements which has been proved to be effective in ore-prospecting practice. Based on expelience gained by laboratories of various geo-logical parties belonging to Ministry of GeoJogy and Mineral Resources, theauthor puts forward a quality-monitoring method for the analysis of 1:50,000samples, several quality parameters and their calculation formulae and statisti-cal techniques. In order to make an objective evaluation of the analytical qua-lity of 1:50,000 geochemical samples, the present paper suggests four qualitygrades (excellent, good, passable and substandard) and their respective qualityparameters.