Hb Val de Marne [alpha 133(H16)Ser-->Arg] was found in a French family during a neonatal hemoglobinopathy screening program. The abnormal hemoglobin was found, within a few months interval, in two newborn children who were first cousins. In the children as well as in the parents carrying this hemoglobin variant, the red cell parameters were normal. Hb Val de Marne, isolated by isoelectrofocusing, displayed a slightly higher auto-oxidation rate than Hb A. Its oxygen affinity was increased 1.7-fold in comparison to that of Hb A. The heterotropic effects were normal.