Angular leaf spot (Pseudomonas syringae pv tabaci) is a serious problem in flue-cured as well as air-cured tobacco, ready for harvesting, in South Africa. The disease has a detrimental effect on the quality of the tobacco leaf. Because no chemicals are registered for the control of angular leaf spot on mature tobacco in South Africa, the objective of this study was to find a compound, preferably systemic, which would effectively control angular leaf spot in the field. Field trials were done over a period of four years in commercial plantings of susceptible flue-cured and air-cured tobacco in areas of South Africa where angular leaf spot occurs naturally and regularly. Contact compounds, such as Xanbac and a quarternary ammonium biguanidine salt were compared with a compound inducing systemic activated resistance (SAR). The theory that potassium induces resistance in leaves was also tested by including a foliar spray containing a liquid organic potassium complex. Results obtained, showed a marked decrease of leaf spot symptoms especially with a combination of the resistance inducing compound and the potassium complex. To a lesser extent a decrease in symptoms was also found with the quarternary ammonium compound. Green leaf mass was also higher for both treatments when compared with the untreated control plots. The use of especially the resistance inducing compound/potassium complex combination could be a big advantage to the farmer for the control of angular leaf spot in commercial tobacco plantings.