The recognition of the eosinophilia-myalgia syndrome associated with L-tryptophan in the United States during 1989 as a disorder resembling the previously described 1981 toxic oil syndrome of Spain has established an increased level of consciousness regarding drug and toxin associated diseases. Both of these disorders were characterized by the development of acute and chronic multisystem features that parallel many idiopathic connective tissue diseases. Common manifestations have included generalized myalgias, fever, transient pulmonary infiltrates, and xerostomia during the early months followed by late stage neuromuscular and cutaneous disease. The most conspicuous laboratory abnormality was a peripheral eosinophilia. One of the most striking clinical findings has been scleroderma-like skin disease manifesting as diffuse fasciitis or hidebound induration. A sensory neuropathy and proximal myopathy in association with skin thickening have established these syndromes as chronic disabling diseases for many of their victims. Mononuclear perimysial and epineurial infiltrates have been distinctive pathological findings. Although the etiology of the eosinophilia-myalgia syndrome and the toxic oil syndrome are unknown, there is epidemiologic evidence to support the presence of contaminants in L-tryptophan and rapeseed oil, respectively, as the causative agents. No therapy has been demonstrated to arrest the evolution of the chronic sequelae in either disorder.