  A seismological study of the pulsating PG1159 stars PG2131+066 and PG
1707+427 is presented. We perform extensive adiabatic computations of g-mode
pulsation periods of PG1159 evolutionary models with stellar masses ranging
from 0.530 to 0.741 Msun. We constrain the stellar mass of PG2131+066 and PG
1707+427 by comparing the observed period spacing of each star with the
theoretical asymptotic period spacings and with the average of the computed
period spacings. We also employ the individual observed periods to find
representative seismological models for both stars.
