Abstract
This paper reviews the mathematical procedures for an analytical representation of linear compartmental systems and the radiation dosimetry of internal organs in terms of matrices and vectors. The features characteristic for internal dosimetry, such as the various forms of intakes, subsystems (e.g., lung, gastro-intestinal tract), and decay products are also discussed. The ICRP concept of internal dose calculation is translated into matrix notation and its application demonstrated by calculating the radiation doses from the ingestion of 40K.