An investigation of the dinitration ofp-cymene (4-isopropyltoluene) has been carried out, with particular regard to determining the effects of varying the temperature, the nitric acid, sulphuric acid, and water contents of the system, the rate of addition ofp-cymene, and the stirring time upon the yields of 2,6-dinitrocymene and 2,4-dinitrotoluene. Optimum nitrating conditions have been determined and the relative constancy of the dinitrocymene: dinitrotoluene ratio over a wide range of conditions has been established. Yields of the order of 55% dinitrocymene and 25% dinitrotoluene have been obtained. Various theories are offered with a view to explaining some of the more important observations.