Iron is an essential element in life. In man, iron disturbances are a cause of abnormalities. This study is interested in one kind of these abnormalities called animia of chronic diseases which is a special kind of anemia observed in many chronic diseases, and is characterized by mild hypoferremia with normal or increased iron stores (in contrast with simple iron deficiency anemia which is characterized by the absence of iron stores). In this study,cancer, tuberculosis and rheumatoid arthritis were chosen as example malignancy, chronic infection, and chronic inflammation respectively. This study, using hematological parameters (hemoglobin concentration, total iron binding capacity (TIBC)) which reflect TRF and serum ferritin concentration, aims to: 1- Know the compatibility of anemia of these diseases to anemia of chronic disease criteria. 2- Estimate the efficiency of these hematological parameters as diagnostic tools from healthy subjects. 3-Estimate the efficiency of these hematological parameters in differentiation between these diseases. With respect to the first goal, the research gave an absolute compatibility in tuberculosis and cancer groups. Rheumatoid arthritis fail to give a good compatibility as in the other two groups. Anemia of it may coexist with simple iron deficiency anemia. Research results with respect to the second goal succeeded to supply several parameters that have efficiency in detecting the diseased from healthy subjects. Lastly, with respect to the third goal, serum ferritin proved its efficiency with high significance to differentiate these diseases from each other.