The rise of human population has crossed all strides in the beginning of 20th century with the result scientists had to employ all tactics to feed the rising population to overcome this use of pyrethroids increased tremendously. Indoor application of pyrethroids, which is often carried out without adequate expert knowledge, may lead to high pesticide residues, often combined with health hazards for the people concerned. Objective of this book is to explain the toxic potential and neuro-toxic effects of the pyrethroid. Hafen 20EC (Fenvalerate), a synthetic, cyno group pyrethroid is extensively used in agriculture, forestry and in household products because of its high activity against a broad spectrum of insect pests, its low animal toxicity and its lack of persistence in the environment. This book help to evaluate Neuro-toxic and biochemical effect of Hafen 20EC on the blood of albino rat because blood maintains the inner homeostatic mechanism and transport nutrients and gases. This book is very useful to the students of toxicology and research scientists.