Sickle cells are abnormal RBCs with bipolar pointed ends and altered rheological properties. They are characterized by the presence of abnormal hemoglobin S. Hb S imparts sickle shape when the oxygen tension is reduced. Clinical significance: Sickle cells are diagnostic feature of the abnormal hemoglobin - Hb S. They are seen in Homozygous and heterozygous states of Hb S gene. Double heterozygotes conditions such as Hb S gene along with Hb C/Hb D/?-Thalassemia. We express our sincere thanks to Dr. Poornakala S for her contribution & support in this.