The productions of beta-exotoxin from sixteen Bacillus thuringiensis strains were examined by Micrococus flava primarily, and then measured by spectrophotometer during culturing in Conner and Hansen mineral salts medium at 28$^{circ}C$. Also the toxic effects of the toxin to mice were checked. The growth of Bacillus thuringiensis K2 and BTK2-T1, -T13, -T33 and -T40 got into stationary phase at 6 hour culture and then maintained it up to 48 hours without severe fluctuation. The production of beta-exotoxin from the strains, BTK2, BTK2-T1, -T13, -T17 and -T33 appeared at 6 hour culture and the amounts of the toxin were about 40 $mu extrm{g}$/$mell$ at 6 hour culture, approximately 70 $mu extrm{g}$/$mell$ at 12 hours, approximately 85$mu extrm{g}$/$mell$ from 24 hours to 48 hours. At 48 hour-culture, BTK2 produced 80 $mu extrm{g}$/$mell$ of beta-exotoxin (5.5$ imes$10$^{8}$ cells/$mell$, BTK2-T13 produced 84 $mu extrm{g}$/$mell$ (4.3$ imes$10$^{8}$ cells/$mell$), BTK2-T17 produced 87$mu extrm{g}$/$mell$ (1.4$ imes$10$^{8}$ cells/$mell$), and BTK2-T33 produced 84 $mu extrm{g}$/$mell$ (4.9$ imes$10$^{8}$ cells/$mell$). All other serotypes also produced beta-exotoxin. At 48 hour culture, BTK-37 produced 88$mu extrm{g}$/$mell$ (6.1$ imes$10$^{8}$ cells/$mell$), BTK-35 produced 81 $mu extrm{g}$/$mell$), and the rest of them produced less than 70 $mu extrm{g}$/$mell$. To check the toxicity of beta-exotoxin and B. thuringiensis, the cultured media with microorganisms were inoculated to mice by per os, intraperiloneal, subcutaneous and intracerebral injection, and nasal cavity inoculation for 30 days. However, the toxin did not kill all of the treated mice.