In many parts of the developed world, the sale and use of phosphide is under strict regulations with adequate training of workers being a major perquisite before its use. In Nigeria this chemical is commonly available and in most cases users are largely untrained, therefore contamination of cowpea with residual phosphide post-fumigation does occur. The aim of this study is to determine the impact of phosphide residue contamination on organs such as brain, lung and heart. Six rats per group were used for this study. The rats in the first and second groups received phosphide residue contaminated and uncontaminated cowpea respectively, while the rats in the third group were fed untreated cowpea and served as control. Tissues (brain, lung, heart) were fixed in 10% formal saline for routine histological techniques and Haematoxylin and Eosin staining technique was used. Feeding of rats with phosphide residue contaminated cowpea resulted in significant damage to all examined tissues. Examination of different sections revealed severe congestion of the meninges (brain); severe congestion at the interalveolar septum with diffuse hemosiderosis (lung); and congestion of coronary vessels (heart) in rats fed cooked phosphide-residue contaminated cowpea. The rats in treated but uncontaminated cowpea and untreated cowpea groups exhibited no visible lesions in all tissue-sections examined. This study has revealed that the erroneous belief among illiterate grain merchants that phosphide residue is harmless should be discarded and proper training of users of this chemical should be encouraged to prevent many of the anomalies associated with cowpea fumigation in Nigeria.