At present, organophosphorus compounds (OP) are considered some of the most toxic substances synthesised by man. These compounds are widely used in agriculture, residential gardening and in pest control programs, as well as in veterinary practices of the modern world. The primary toxicity of organophosphates is associated with the inhibition of acetylcholinesterase in the central and peripheral nervous system, resulting in acetylcholine accumulation and consequently disrupted neurotransmission. In this book, Chapter One provides an overview of recent studies regarding toxic effects of organophosphates, the methods of their removal, and detoxification in live organisms. Chapter Two summarizes the results of monitoring agricultural products for the presence of organophosphorus pesticides, putting a special emphasis on potential ways for reduction of their levels. The final chapter focuses specifically on the structural features, applications, toxicity mechanisms and effects of exposure on human health of fenitrothion, a non-systemic organophosphorous insecticide.