An inflammatory disease is sometimes suspected despite a normal erythrocyte sedimentation rate (ESR). When this dissociation is present, the reasons for the lack of ESR elevation, which concern the red cells, the plasma and the laboratory techniques, must be excluded, the reality of the inflammatory syndrome being then confirmed by assay of the inflammatory proteins. However, an inflammatory syndrome is missing in 5 to 10 percent of inflammatory diseases, more frequently in cases of polymyositis or scleroderma, less frequently in those of giant cell arteritis. Little information can be found in the literature, concerning the missing inflammatory syndrome. Does it confer peculiar semeiological or prognostic features? Is the dissociation related to the patient, as would appear in some special cases, or to the disease, as suggested by the small rise of the C-reactive protein in acute episodes of lupus erythematosus? The absence of inflammatory syndrome is a source of diagnostic problems when the symptoms are atypical or when there are no specific signs of the suspected disease. Differential diagnoses, especially non-inflammatory diseases, must then be carefully discussed. Improving our knowledge of the missing inflammatory syndrome would require the creation of this key-word.