Paraphenylene diamine (PPD) is commonly used in the Sudan as hair dye and to intensify Henna colour. Several cases of poisoning with this compound have been reported in humans. Therefore, in the present work, we have examined the haematological, pathological and biochemical actions of PPD in rats and chickens. We also attempted to extract and detect PPD in tissues from treated rats and chickens. The toxic effects of PPD were qualitatively similar in the two species, but the onset of toxicity was faster and incidence of mortality higher in rats than in chickens. The clinical signs of toxicity included anorexia, decreased mobility, hind leg weakness and death. Histopathologically, PPD caused congestion, fatty change and necrosis in the liver, kidney, heart and muscles. This was accompanied by significant increases in plasma enzymes and metabolites indicative of tissue damage. Haematologically, there was also significant decreases in the packed cell volume, haemoglobin and erythrocytes counts. PPD could not be detected in the tissues of treated animals, probably suggesting that metabolite(s) of PPD and not the parent compound were responsible for the toxicity.