Abstract: In the past 6 years, 278 pesticide products adulterated with unregistered substances were reviewed. The greatest number of these products was insecticides, and their formulations belonged mostly to the emulsified EC and water-soluble powder WP. They were registered for applications on vegetables, fruits, tea,rice and cotton. The adulterants were frequently organophosphorous and pyrethroids. Some of these products claimed to control the same pests as do the legal products, while other might even extend their coverage. Possible harms of the illegal act are discussed and recommendations to alleviate such practice by measures including enforcing product monitoring on the market, establishing standards and regulations and increasing penalty for violators are discussed.