Six male and three female patients previously iron deficient after a partial gastrectomy were investigated using a whole body counter to measure their percentage (59)Fe retention. No significant difference in iron loss between postgastrectomy patients and controls was found in the majority of subjects over a study which lasted from 175 to 225 days. The detection of increased free iron loss requires a more sensitive double isotope faecal recovery method. Two patients developed acute bleeding during the study and the whole body counter provided clinically useful data on blood loss. If patients develop gastrointestinal blood loss after partial gastrectomy either a recurrent ulcer or a site of blood loss elsewhere (eg, in the lower bowel) should be excluded.