Low molar mass (Mn Ñ < 4000 g.mol -1 ), narrow molar mass distribution (Mw Ñ /Mn Ñ =1.1-1.3) linear α-(tert-butyl) ω-(tert-chloro) and α-cumyl ω-(tert-chloro) oligoisobutylenes (PIBs) were synthesized using two initiating systems: 2,4,4-trimethyl-pentan-2ol (TMPOH)/BCl 3 /-40¡C and 2-phenylpropan-2-ol (CumOH)/-BCl 3 /-70¡C in the presence of an efficient electron-pair donor (ED), 1-methyl-2-pyrrolidinone (NMP) in methyl chloride. The kinetics of oligomerization were investigated. In these two systems, similar polymerization mechanisms were observed with, nevertheless, a slight difference of growing species behavior in the early polymerization steps. The initiation and propagation rate constants were determined; their values are low showing that the addition of NMP to these initiating systems leads to controlled carbocationic polymerizations. Moreover, the living character of the polymerization was demonstrated.