The kinetics of transesterification of dimethyl terephthalate with ethylene glycol performed in the presence of catalysts such as: Pb, Zn, Mg, Co, and Mn acetates and a mixture of Mg, Mn, and Zn acetates has been studied in semibatch conditions. T h e catalytic behavior of Sb203 has been proven, too. T h e performance of the different catalytic systems has been investigated following both the amount of methanol released during time a n d t h e evolution with time of the concentration of any kind of oligomer formed as consequence of the reaction. T h e oligomers obtained were separated, identified, a n d quantitatively determined by H P L C analysis. In this way, information have been achieved on both the activities a n d selectivities of the different catalysts. T h e experimental data have been interpreted through a classic kinetic model based on a complex reaction scheme. Despite the complexity of the model, only two kinetic parameters and two equilibrium constants are necessary to simulate the kinetic behavior of all the oligomers. A kinetic constant (K,) is related t o the reaction of a methyl group with a hydroxyl of ethylene glycol, while the other ( K 2 ) corresponds t o the reaction of a methyl group with a terminal hydroxyl of a growing chain. T h e Mn, Pb, and Zn acetates have shown comparable high catalytic activities; however, the Mn selectivity to give oligomers with hydroxyl-hydroxyl terminal groups is better and similar t o t h a t shown by Co and Mg acetate, at a lower activity. Sb203 has a very low activity in transesterification but this activity could be important to eliminate the residual terminal methyl group during the polycondensation step. T h e catalytic activity of the mixture of Mg, Mn, and Zn acetate was greater than t h a t shown by each component the mixture, while its selectivity was comparable with that of M n a n d Mg acetate. (