Haemoglobin Bart’s was detected and quantitated in 42 babies during a survey of cord blood from neonates of Mediterranean origin. The distribution of Hb Bart’s levels for the group appeared to be bi-modal, with modes at 2.0% and 5.5%. Haematological data obtained from 21 babies during the first week of life showed a highly significant reduction in average MCV (86.3 +/- 7.7 fl) and MCH (27.8 +/- 6.0 pg) in comparison with a control group of babies. However, there was no significant correlation between these parameters and Hb Bart’s levels. Haematological data were available on 57 parents of the Hb Bart’s babies and HbH preparations were positive in 28 cases (49%). Examination of red cell indices showed a highly significant reduction in the average MCV and MCH of parents with positive HbH preparations, and a diagnosis of alpha-thalassaemia (based on the presence of HbH inclusion bodies and reductions in MCV and/or MCH) was made in at least one parent in the majority of couples with both partners tested, suggesting that alpha-thalassaemia trait in people of Mediterranean origin is generally associated with detectable haematological changes.