SummaryTarget cell characteristics in thalassemia are described. This abnormal red cell may be seen in other diseases than thalassemia and can be acquired.Hyperbilirubinemia can be a factor favouring the apparition of this abnormality. Other important factors are macrocytosis of medullary origin in liver parenchymatous diseases, and red cell hypochromia.Clinical cases illustrate these theoretical considerations.Red cell diameter measurement and search for target cells are valuable tools in diagnosis of liver disease.