Abstract: In this paper the error sources in analysis of soil samples in ecological geochemistry survey are investigated. The selection of the analytical methods and their optimization in high precision measurements, the standard reference materials used in X-ray fluorescence analysis, the effect of gross errors on F-test are discussed. Based on the discussion some proposals on processing of maximum and minimum values in measurements, reasonable utility of internal control samples, setup of the warning limits for measurement quality control, verification of the total components and spot check for abnormal values are put forward.