The influence of urokinase and oxygen availability on growth, siderophore, protease and lipase production in Burkholderia cepacia and non-mucoid (PA01) and mucoid (PaWH) strains of Pseudomonas aeruginosa was assessed for cells grown in batch culture under iron-restriction. Siderophore production decreased with increasing concentration of urokinase in B. cepacia independent of oxygen availability but decreased in both strains of P. aeruginosa only under oxygen-depleted conditions. Protease activity was enhanced for all three strains irrespective of oxygen content whereas lipase production increased in B. cepacia and decreased in PA01 under both sets of growth conditions and varied with oxygen availability in PaWH. The evidence presented suggests that urokinase could contribute to the pathophysiology of pulmonary infections.