alpha-thalassaemia and beta-thalassaemia traits are two commonly encountered haemoglobinopathies in South East Asia. Both present with hypochromia and microcytosis. The use of modern electronic or optical cell counters which measure accurately the red cell parameters has allowed for an initial quick screening for the presence of thalassaemia. Seven red cell parameters were measured by the Technicon H1 cell analyser--red cell count, Hb, MCV, MCH, red cell distribution width (RDW) and haemoglobin distribution width (HDW). Discriminant analysis of these parameters and zinc protoprophyin (ZP) indicates that in healthy individuals, alpha-thalassaemia can be differentiated from beta-thalassaemia with an accuracy of 86% when analysed as a group. In hospitalized patients the accuracy dropped to 71% due to biases of concomitant illness. The two most important parameters for indicating differences between alpha- and beta-thalassaemia are MCV and ZP. The results confirm further that though alpha- and beta-thalassaemia have the same phenotypic expression they differ in their biology.