Objective:The present work aimed to measure the levels of telomerase activity in peripheral mononuclear cells taken from patients with SLE and RA.Method: Forty patients and ten normal subjects were included in this study. The patients were divided into two groups. Group one included SLE patients 20 females and 2 males. Group two included RA patients 15 females and 3 males. The control group included 5 females and 5 males. Patients and controls were subjected to full history taking, complete clinical examination, laboratory investigations including the assay of telomerase enzyme activity both by telomeric repeat amplification protocol (TRAP) by PCR-ELISA and real time PCR by light cycler.Results: Telomerase enzyme was significantly higher in patient group than in control group. Telomerase activity was high in SLE group but was not detected in RA group. In SLE group, the telomerase enzyme was significantly higher in untreated than in treated group. Telomerase enzyme showed significant correlation with SLEDAI which indicate disease activity where telomerase enzyme was detected in patients with high SLEDAI.