Second instar larvae of Spodoptera. littoralis were fed on caster bean leaves treated with different concentrations of Dipel (Bacillus thuringiensis var. kurstaki).  after 72 hours of treatment (estimated LC₅₀)  Regarding the LT₅₀ values a negative relationship could be detected between the applied concentration of Dipel and LT₅₀ value; i.e. the LT₅₀ was shortened with the increase in Dipel concentration.  The LT₅₀ values being 14.17, 8.81,5.99 and 2.40 days for the used concentrations of  8, 12, 16 and 20 × 10⁴ I.U. The second instar S. littoralis larvae were fed on fresh caster bean leaves treated with different concentrations of Dipel + 05 % Amino. , the corrected mortality percentages after 3 days increased by increasing concentration   ranged from 40.00 to 90.00 % at the concentrations of 8 to 28 × 10⁴ I.U., the LC₅₀ value was 11.31 × 10⁴ I.U.  for S. littoralis after 3 days., comparing the effects of the two treatments (Dipel and Dipel + 0.5% Amino) on the mortality percentages at same concentration used, Diple + 0.5 % treatment led to increase the percentages of mortality in all concentrations used and thus led to decrease the value of LC₅₀ from 17.14 to 11.31 × 10⁴ S.U. and shortened also the values of LT₅₀ from 14.7, 8.81 and 5.99 to 6.66,3.88 and 2.18 days at concentration of 8, 12 and 16 × 10⁴ I.U., respectively,   The LC₅₀ of Diple2x + 1% Amino Acid was 15.59× 10⁴ I.U.  72 hours post treatment , a negative relationship could be detected between the applied concentration of Dipel + 1% Amino and. the LT₅₀ was shortened with the increase in treatments concentration. These values were 11.61, 7.97, 3.99, 3.07 and 1.72 days for the used concentrations of 8, 12, 16, 20 and 24 × 10⁴ I.U. , respectively . LC₅₀ of Diple2x + 1.5% Amino Acid was 16.06 × 10⁴ I.U. after 3 days of treatment. and LT₅₀ values.   were 14.12, 6.73, 3.13 and 1.69 days at concentrations of 8,12,16 and 20× 10⁴ I.U. , respectively.. The LC₅₀ of Diple2x + 2.5% Amino Acid was was 16.62 × 10⁴ I.U.. After3 days from treatment while the LT₅₀ values were 11.18, 6.56, 4.15 and 2.80 days at concentrations of 8, 12, 16 and 20 × 10⁴ I.U., respectively. , LC₅₀ value of Dipel 2x + 0.5 % amino (11.31× 10⁴ I.U.) was the most effective one among all treatments ,also, led to shortened  the values of LT₅₀ (6.66, 3.88 and 2.18 days for the used concentrations of 8, 12 and  16 × 10⁴ I.U., respectively