The results of measurements of the dielectric constant of TlGaSe2 in the temperature range of successive phase transitions in various regimes, including the measurements after annealing the sample at a fixed temperature in the incommensurate phase are presented. A noticeable influence of the sample prehistory on the dielectric behavior of TlGaSe2 has been revealed. Peculiarities of the anomalies in the temperature dependence of the dielectric constant corresponding to structural phase transitions at the temperatures of 108 K and 115 K are discussed. It is suggested that these anomalies can be interpreted as successive lock-in commensurate transitions due to incommensurate structures appearing at 120 K and 242 K respectively. (c) 2005 Elsevier B.V. All rights reserved.