[en] This paper is focussed on the results obtained in the last three external quality assurance cycles conducted for the TLD units at six nuclear power stations and the various measures taken for the improvement of the quality and reliability of the personnel monitoring service conducted by these units. In addition to the ANSI criteria the trumpet curve analysis method was introduced for testing the performance of the TLD units. The performance of all the units had been well within the permitted tolerance level and for some units highly satisfactory performance with a tolerance level value below 0.1 was observed. A constant interaction with concerned implementing units and efforts of the TLD units in implementing new suggested measures resulted in bringing down the number of TLD-DRD discrepancy cases by about a factor of 2 in the past four years. (author)