The present study aimed to investigate the effects of RNAi-mediated reduction in human telomerase reverse transcriptase (hTERT) expression on apoptosis and lung cancer cell proliferation. A number of cell lines, including 95D, were used. hTERT mRNA levels were detected, and the RNA concentration was calculated. MTT assay was used to detect the inhibition of cell proliferation. The siRNA with the highest suppression rate, siRNA-1, was transfected into 95D cells at three different concentrations (50, 80 and 100 nmol/l). The levels of hTERT mRNA in cells transfected with 50 nmol/l siRNA-1 were not significantly different from those of the negative control-transfected cells (P>0.05), whereas both 80 and 100 nmol/l siRNA-1 showed significant reductions in hTERT mRNA compared to the negative control cells (P<0.01). hTERT levels in the 80- and 100-nmol/l groups were not significantly different (P>0.05). Compared with the control cells, cells transfected with 50, 80 or 100 nmol/l siRNA-1 showed higher fractions of apoptotic cells 48 h post-transfection (P<0.01), although the apoptotic fraction in cells transfected with 50 nmol/l siRNA-1 was not significantly different compared to that in cells transfected with negative control siRNAs (P>0.05). Moreover, the 80- and 100-nmol/l-transfected cells showed significantly increased apoptotic indices (P<0.01). MTT results indicated a time-dependent inhibition of siRNA-1- transfected cell proliferation starting at 12 h and lasting through 48 h post-transfection; the inhibition was attenuated by 72 h post-transfection. The high levels of hTERT mRNA in all human lung cancer cell lines tested suggest that telomerase plays a role in lung carcinogenesis, and this hypothesis was strengthened by the data showing that the siRNA-mediated reduction in hTERT mRNA caused apoptosis and an inhibition of the proliferation of lung cancer cells.