Over the past years, the use of administrative data in both official statistics and academic research has grown. This development has made the problem of assessing the quality of administrative sources for statistical use increasingly important. Two of the main aspects of this are validity and reliability of measurement. Although this problem is often mentioned in qualitative terms, so far, not much research has been done on methods that assess the validity or reliability of administrative variables in a quantitative way. The objective of this paper is to describe a quantitative method for estimating validity and to present results obtained with this method in a simulation study.