Water turnover rates of Tasmania devils, Sarcophilus harrisii, were measured under standardized conditions by use of tritiated water. Total body water of lactating females was lower than in non- lactating animals, while water turnover rates per kilogram were not significantly different, due to a higher rate constant for lactating animals. Mean water turnover rates were considerably higher than predicted from other marsupial studies. Statistical analysis of data from 13 species of marsupial and 27 eutherian species showed habitat to have a far greater effect on standard water turnover rate than phylogeny.