The chemical deposition of pyrethroid insecticides applied in water or urea solutions (commercially available as 22% urea) on cotton was investigated in six experiments, two with aerial application and four involving ground application. Chemical deposition was based on micrograms of pyrethroid recovered from gas chromatographic analysis of hexane rinses of cotton leaves and aluminum pans at various intervals following application. In the four ground application experiments, there was a 35-75% reduction in the amount of pyrethroid recovered immediately after treatment in a urea solution compared to application in water. Data from two of these experiments indicated that even though there was less pyrethroid recovered from cotton leaves immediately after application in a urea solution (compared to application in water), the pyrethroid in the urea solution was relatively more stable over a 24 hour period. Results of the two experiments involving aerial application were conflicting. In the first experiment, the data followed trends similar to that obtained in the four experiments involving ground application, i.e. the amount of pyrethroid recovered immediately after application was less when applied in the urea solution compared to application in water.However, results of the second experiment indicated that similar amounts of pyrethroid were recovered regardless of whether the pyrethroid was applied in water or urea solutions. The biological activity of organophosphate and pyrethroid insecticides applied in water or urea solutions was evaluated in four experiments. The aphicidal, Aphis gossypii Glover, activity of organophosphate insecticides was reduced by at least 50% when applied in a urea solution compared to application in water in two experiments. The other two experiments examined the efficacy of a pyrethroid in water or urea solutions against tobacco budworm, Heliothis virescens (F.). Results of these experiments indicated significantly less mortality from the pyrethroid applied in a commercial urea solution was observed compared to application in water. However, the biological activity of the pyrethroid in a freshly prepared reagent grade urea solution was not significantly different from that of the pyrethroid in a water solution. In a preliminary test, the flow rate of a commercially available urea solution was determined to be 8% less than the flow rate of water at the same pressure. Except for the decreased flow rate, the reason(s) for the decreased deposition and biological activity of insecticides applied in urea solutions is unknown.