This is a book of a research work done in the Biology Department at Science College of King Abdulaziz University in Jeddah City, Saudi Arabia. It includes the prevalence study of head lice between the girl students of some public and private elementary schools, as well as it concerns about testing some natural substances as anti-head lice, that wood tar solution and garlic juice were the most effective materials. The head lice prevalence was greatly affected by the socio-economic status, the crowding criteria and by the student's hair characters and their hair cleaning habits. This effort is considered as a valuable reference in this part of study.