Seven hundred and ninety-five people, (96% of whom were of Greek origin) were screened for thalassaemia trait. A prevalence rate of 7.1% for beta-thalassaemia carriers was found. The red cells of individuals with the alpha-1-thalassaemia, beta-thalassaemia, and haemoglobin Lepore traits all had a mean corpuscular volume (MCV) of less than 76 fL and a mean corpuscular haemoglobin (MCH) of less than 25 pg, thus confirming the usefulness of these indices as a preliminary thalassaemia screening test. However, in three of the six people provisionally diagnosed as having delta-beta-thalassaemia trait, an overlap of MCV and MCH values with the normal range occurred. Community attitudes to the survey and its implications are discussed.