Hole drift mobilities (mu) were measured in a series of triphenylamine (TPA) molecules and oligomers dispersed into bisphenol-A polycarbonate (PC) by conventional time-of- flight techniques. The transport molecules were oligomeric triphenylamine (OTPA) containing 8-10 TPA units TPD and TPA. In PC doped with 50 wt percent OTPA, TPD, and TPA, (mu) values were of 1 X 10-7, 1 X 10-5, and 7 X 10-6 cm2/(V S) accordingly, at the electric field of F equals 5 $ MUL 105V/cm and room temperature. In order to elucidate the relationship between structure of transport site and mobility, the molecular orbital calculations were made for the TPA, TPD and OTPA molecules. For the calculations, the PM3 method was chosen because it gave better agreement between calculated and experimentally parameters than the AM1 method for the molecules studied. The result obtained from the hole mobility measurements and the quantum chemistry calculations demonstrate that the N-Ph-Ph-N fragment is a transporting center for both TPD and OTPA molecules. For OTPA, the end fragments of the molecule appear as transport sites.