Use of pesticides including insecticides, fungicides and herbicides on a large scale can eventually lead to contamination of the environment and accumulation in food chain. So these may lead to a hazardous atmosphere for humans and animals. Modern pesticides pyrethroids have replaced older organo-chlorine pesticides. These pyrethroids have more efficiency and low bio-accumulation but still have serious health effects. Many countries, including Pakistan, are facing problems of dengue fever and malaria, and alpha cypermethrin is effective against vectors of these epidemics. Despite prohibition by World Health Organization, pyrethroids are being extensively used in Pakistan. Millions of poisoning cases and casualties are reported each year worldwide. Alpha cypermethrin, a pyrethroid, is more effective against pests and also can lead to increased intoxication of environment and consequently higher chances of intoxication of non-targeted organisms. This book highlights the adverse effects of alpha cypermethrin on male reproductive system specifically on testicular histopathology in adult male rabbits as well as changes in body weight, gonadosomatic indices and behavior.