Volatilities of 2-chloro-4,6-bis(ethylamino)-s-triazine [simazine], 2-chloro-4-ethylamino-6-isopropylamino-s-triazine [atrazine], 2-chloro-4,6-bis(isopropylamino)-s-triazine [propazine], 2-methoxy-4,6-bis(isopropylamino)-s-triazine [prometone], 2-ethylamino-4-isopropylamino-6-methylmercapto-s-triazine [ametryne], 2,4-bis-(isopropylamino)-6-methylmercapto-s-triazine [prometryne], and 2-chloro-4-diethylamino-6-ethylamino-s-triazine [trietazine] were studied at different temperatures. In descending order at 25 C the relative volatilities of the herbicides from nickel-plated planchets were prometone ≅ trietazine > atrazine ≅ ametryne ≅ prometryne > propazine ≅ simazine. Prometone losses from five soils appeared to be directly related to per cent sand and inversely related to per cent clay and organic matter. Atrazine and simazine losses from the same soils appeared to be less influenced by soil properties than prometone. All seven s-triazines were examined at one temperature on wet and dry Tifton loamy sand. Moisture level affected both the amount of compound lost and the relative order of loss among compounds. Conversion of atrazine and prometone to their corresponding hydroxy analogues was a practical method for preventing vapor losses from planchets.