Collagen-vascular diseases are an ill-defined collection of syndromes that have certain points of similarity, among which the most striking are fibrinoid necrosis of collagenous tissue and involvement of various subdivisions of arteries by an inflammatory process. Some diseases emphasize one aspect and some the other. Because blood vessel inflammation and other abnormalities found in the collagen diseases may also be found to a certain extent in some patients with RA, some investigators prefer the term “rheumatoid-collagen diseases.” Others do not wish to use the designation collagen disease at all. Some justification to group together these often quite dissimilar syndromes is the overlap in signs, symptoms, and laboratory abnormalities between the different conditions as well as the probability that their basic etiology is a disorder involving immunologic hypersensitivity. Those conditions usually included in the connective tissue (“collagen”) disease group will be discussed first; then other diseases involving joints; and finally, certain conditions primarily due to vasculitis.