The solubility of 3,4-dinitrotoluene (3,4-DNT) in natural filtered seawater with ionic strength = (0.1662, 0.3352, 0.5071, and 0.6820) mol.L-1 and pure water was measured at temperatures ranging between (277 and 314) K. The solubility in seawater was lower than that in pure water. The average salting-out coefficient for 3,4-DNT was 0.13 L.mol(-1), which is consistent with measurements for other isomers of dinitrotoluene. The salting-out coefficient did not show any significant variation with temperature over the range examined.