Our study has been performed in Agouza Rheumatology and Rehabilitation Armed Forces Centre and included Sixty (60) patients with sciatica (associated or not with LBP) of both sexes, and age range between 30 and 64 years, and 20control individuals matched for both age and sex. Patients were subdivided into three groups according to the electrical modalities applied: Group 1 (n= 20) received 30 minutes of IF current. Group 2 (n= 20) received 30 minutesof D.D current. Group 3 was subdivided into Subgroup 3A( n= 10) received 30 minutes of AL-TENS, and Subgroup 3B (n=10) received 30 minutes of Conventional TENS.Mean plasma β-endorphin levels were measured before, after having six sessions, and at the end of the treatment program that included twelve sessions. Mean V.A.S of pain was also measured before and after sessions, andcorrelations of V.A.S of pain with the plasma BE levels were also done.Our study concluded that the mean plasma β-endorphin level increased significantly after 6 and after 12 sessions of treatment in Group1, Group2, and Subgroup 3A receiving IF, D.D, and AL-TENS respectively. This increase wasassociated with a significant decrease of V.A.S. No significant increase in plasma β-endorphin levels occurred in Subgroup 3B receiving Conventional TENS after 6 or after 12 sessions, also no significant decrease of mean V.A.S. Also this study demonstrated that the increase in 1 mean plasma β-endorphin level was significantly higher in Group1 (IF gp) than groups 2, or 3A after the 6th or 12thsessions, whereas no significant difference in plasma β-endorphin levels was found between Group 2 and Group 3A after the 6th or the 12th sessions. In our study there was a significant negative linear correlation between the increased plasma BE levels and lowered V.A.S. of pain after the 6th and 12th sessions in Gp1, Gp2, and Gp3A. Also a negative linear correlation with R.O.D.Q after the 6th and 12th sessions. As regards the Conventional TENS group of patients there was no negative linear correlation of the VAS with the plasma BE levels after six sessions,less negative linear correlation after twelve sessions. The present study also revealed that there was a negative linear correlation ofplasma BE levels with SLR sign after the 6th session in Gps 1,2,3A, where the positivity of this sign decreased as it is considered positive from 30-50 degrees. After the 12th session there was also a significant negative correlation with SLR test in Gps 1,2,3A. Whereas no correlation was found with the R.O.D.Q or SLR Sign in Gp 3B receiving Conventional TENS after six or twelve sessions. Theresults are correlative with the mechanism of action of Conventional TENS.So, IF current appears superior to the other two electric modalities in the relief of pain through the release of β-endorphin. Our study also demonstrated that AL-TENS and not Conventional TENS works through the release of β-endorphin.