The phase transition of a homologous series of liquid crystalline polyesters was studied under hydrostatic pressures up to 300 MPa by using a high-pressure DTA apparatus. The thermotropic polyesters, abbreviated as PB-n (where n is an even number of methylene units), were prepared from 4,4’-dihydroxybiphenyl and aliphatic dibasic acids containing an even number of methylene groups from 8 to 22 units. The T vs, P phase diagrams of the PB-10, PB-12, PB-14 and PB-18 polyesters were constructed. PB-10 shows a simple phase transition of crystal (K)-smectic-H(S-H)-isotropic melt (I) over the whole pressure region. PB-12 shows a similar K-S-H-I transition in the low-pressure region below about 100 MPa. At high pressures above 100-120 MPa, however, PB-12 exhibits a T vs, P relation that is different from that in the low-pressure region. The phase diagram supports the existence of the pressure-induced smectic phase which was assigned to be the smectic-B (S-B) phase. The PB-14, PB-16, and PB-18 samples show an additional first-order transition just below the K-S-H transition at atmospheric pressure, The new transition peak increases with increasing space n in the PB-n samples, in contrast to the decrease in the K-S-H transition peak, The transition is a kind of crystal transition between the low- and high-temperature phases, denoted here as K-1 and K-2. The thermal behavior of these samples can be understood as enantiotropic transitions through the K-1-K-2-S-H-I route. They show the same type of T vs. P phase diagram, indicating the K-1-K-2, K-2-S-H and S-H-I transition lines. The phase diagrams indicate that the stable region of the S-H phase broadens with increasing pressure. However, the K-2-S-H transition peak becomes too small to be detected under pressures of 300-400 MPa.