Objective. Telomerase plays an important role in the cellular immortalization of cancers. It contains telomerase RNA and telomerase reverse transcriptase. Telomerase activity may be used to predict the biological behavior of glioma. Methods. Telomerase activity was investigated in consecutive cell line passages in cell extracts taken from DK-MG cell line. Telomerase activity was determined for the 3rd, 6th, 9th, 12th and 15th passages. To detect telomerase activity, cell lysate was extracted by lysis buffer, and telomeric repeat amplification protocol was performed, using a PCR-based TRAP TeloTAGGG Telomerase PCR ELISA PLUS kit (Roche). Total RNA was isolated from cultured cells (Biological Industries). The expression of hTERT and hTR was analyzed by RT-PCR (Qbiogene). Results. Telomerase activity was found to be increased in the later passages of DK-MG cell line, although it demonstrated a fluctuating pattern. Telomerase reverse transcriptase and telomerase RNA expressions were also evaluated to support the telomerase activity. Conclusion. In consecutive passages of DK-MG glioma cell line, increase in telomerase activity may be irregular. As a single parameter, its use at any consecutive passage may be considered a misleading factor for the researcher. The results of our study also pointed out the necessity to check other parameters in addition to telomerase activity in future studies on cancer cell lines such as glioma.