Temporal oscillations of the bromate-4-aminophenol system have been studied in the presence of four different catalysts:tris(1,10-phenanthroline)iron(II) sulfate(ferroin),Ce(III),Mn(II),and Fe(II).Transient temporal oscillations were observed in the four catalyzed systems when the reactions were conducted in a stirred batch reactor.The induction time was prolonged by the presence of ferroin,but it was shortened in the Ce(III)-and Mn(II)-catalyzed systems.On the other hand,the number of peaks was significantly decreased in the presence of ferroin.The development of oscillatory behaviour was found to be more sensitive to the ratio of bromate and 4-aminophenol concentration than to their absolute concentrations.The reaction rates of 4-aminophenol with Ce(IV) and 4-aminophenol with ferritin were measured directly by spectroscopic methods in a sulfuric acid medium. Temporal oscillations of the bromate-4-aminophenol system have been studied in the presence of four different catalysts: tris (1,10-phenanthroline) iron (II) sulfate (ferroin), Ce (II). Transient temporal oscillations were observed in the four catalyzed systems when the reactions were conducted in a stirred batch reactor. The induction time was prolonged by the presence of ferroin, but it was shortened in the Ce (III) -and Mn ( II) -catalyzed systems. Of the other hand, the number of peaks was significantly less in the presence of ferroin. The development of oscillatory behavior was found to be more sensitive to the ratio of bromate and 4-aminophenol concentration than to their absolute temperatures The reaction rates of 4-aminophenol with Ce (IV) and 4-aminophenol with ferritin were measured directly by spectroscopic methods in a sulfuric acid medium.