A case is reported of progressive dementia and a terminal picture of generalized tetaniform contractures. The relationship of the generalized tetaniform contractures to the stiff-man syndrome is discussed. Morphologically, diffuse amyloid deposition was found in the pial and cortical vessels, accompanied by amyloid deposition in the senile plaques in the cortical and cerebellar cortex. Apart from the typical staining and ultrastructural aspects of amyloid, a deposition of material was observed, corresponding in optical and electron microscopy to a paraprotein. This case demonstrated not only the relationship between the deposition of amyloid and the formation of senile plaques, but also sustains the direct connection between amyloid in senile plaques and the paraprotein substances deriving from the blood. The probable relationship between the unusual deposition of paraproteins in the vessels and nervous system and the treatment with immunoglobulins is discussed.