Abstract
As part of a programme designed to investigate experimentally the value of W in the context of neutron dosimetry for radiotherapy, the concept and the practical aspects of tissue equivalence were investigated. The concept requires a knowledge of the composition of human tissue and the effect of any change in the atomic composition of the tissue sample on the absorbed dose measurement. The practical aspects introduce further constraints of experimental safety, convenience, and the need for comparability between workers. This brief paper reviews the essential features of neutron tissue equivalence for radiotherapy and concludes with the results of a computation of relative absorbed dose using various tissue models.