Iurus dufoureius asiaticus, Birula, 1903 scorpions were collected in Mugla province located in the Aegean region, Turkey. There are few number of publications about I.d. asiaticus, and there are no data regarding minimal lethal dose and effects of the scorpion venom till now. This is the first study about toxicity and effects of I.d. asiaticus scorpion venom in mice. Previously, most of the proteins in venom of I.d. asiaticus from Aydin region in Turkey were reported to be between 14 and 205 kDa in size. In this study, we determined the electrophoretic protein pattern of the venom taken from Mugla province to be between 29 and 116 kDa by SDS-PAGE. Intracerebroventricular (i.c.v.) was determined instead of s.c. injection since there were no deaths in any s.c. test groups. The LD(50) of I.d. asiaticus scorpion venom was found to be 47.7 microg/20 g mouse by i.c.v. injection route. After s.c. injection venom, mice were shown any intoxication symptoms. On the other hand, after i.c.v. administration of venom, mice showed symptoms such as excitability, hyper salivation, weakness, paralysis, coma and resulting in death. The possible cause of death could be due to multi-system organ failure depending on the toxic effect of the venom. These both results showed that the venom was not lethal on s.c. injection, but it was lethal on i.c.v. injection. This may imply that the scorpion is of little danger to humans.