The manner in which density and crowding were measured in Melbourne, Australia, was found to be of crucial importance in explaining the observed relationships between these variables and human pathology measures. The more theoretically relevant measures of density and crowding displayed higher correlations with human pathology measures than less theoretically relevant measures. It was concluded that contradictory findings in the literature regarding the importance of density and crowding as determinants of human behaviour can be attributed in part to the failure of researchers to specify measures of density and crowding appropriate to the theoretical models they are testing.