Hypochromic and microcytic red cell morphology is the most commonly encountered abnormality in a clinical laboratory. Most of such cases have iron deficiency anaemia. However, in Pakistan about 5% of the individuals with a hypochromic and microcytic blood picture have the β-thalassaemia trait. These individuals are more than often in a positive iron balance. However iron deficiency (being common) may be associated with the β-thalassaemia trait. This study of serum ferritin levels was carried out on 135 confirmed cases of the β-thalassaemia trait. A ferritin assay was done by a radioimmunoassay technique. The results show that the level of serum ferritin in 100 (74%) cases was within normal limits, in 17 (12.6%) cases it was above the normal range, whereas in 18 (13.4%) cases the level was lower than normal. The importance of serum ferritin estimation in carriers of the β-thalassaemia trait is highlighted.