The objective of the investigation was to evaluate the reliability of the authors´ method of the ratio of i.v. administered radioactivity of 99mTc-DMSA cumulated by the kidneys. The reliability of the method was evaluated by interobserver and intraobserver variability and variability of the ratio of cumulated radioactivity two to three hours after administration. The authors used Kolmogorov- Smirnov´s and Wilcoxon´s tests for two independent samples and the paired t-test. None of the investigated parameters differ significantly at the 5% level of significance. Only the size of the area of interest defined by various assessors differs significantly, though systematically in one direction. Under common clinical conditions the method gives reliable results.

        Key words: 99mTc-DMSA - cumulation by kidneys - calculation - reliability of method