This paper provides an empirical comparison of time-varying technical inefficiency measures obtained from the econometric estimation of different specifications of the stochastic production frontier model. Specifically, ten different frontier model specifications, which are most widely used in empirical applications, are estimated using a balanced panel data set from the Greek olive-oil sector, consisting of 100 farms observed during 1987-93 period. The empirical results indicate that both the magnitude and individual ranking of technical efficiency estimates differs considerably across models.