Diogenes brevirostris was found to be tolerant to low salinities (0,5 - 4,0 %) at a wide range of temperatures (12 to 27°C). Tolerance to temperature and salinity were inversely related. At low salinities (0,5 and 1,0 %) the rate of mortality increased with temperature throughout the range, whereas at higher salinities (1,5 and 4,0 %) temperature had no effect on mortality. These results are discussed in relation to the distribution of D. brevirostris in estuaries. It appears that temperature and salinity tolerance are not solely responsible for limiting distribution of these crabs to estuary mouths.