The study of erythrocyte morphology is of great importance in the field of hemorheology as the deformability of the circulating cells has a fundamental influence on the rheological properties of the blood. Diabetes mellitus, hypertension, dyslipidemia and obesity (mostly central obesity) are the major components of metabolic syndrome. In this review, we focus on the changes in erythrocyte morphology in different components of metabolic syndrome and also discuss the erythrocyte morphology in regards to oxidative stress - a common state of chronic diseases. This article also addresses the problem of inconsistency in the use of nomenclature and technique to identify the abnormal morphology and we recommend the use of standard terminology by all authors.