['General iron supplementation to prevent iron deficiency in infants who are iron sufficient when starting supplementation may adversely affect their health.', 'A secondary analysis to explore the effect of iron supplementation on iron-replete (IR; Hb > or =113 g/L and S-ferritin > or =33 microg/L) or non-iron-replete 6-month-old Indonesian infants participating in a large, randomized trial on iron and zinc supplementation.', 'Among the iron-supplemented IR (Fe-IR, n = 80) infants S-ferritin was, compared to non-iron-supplemented (NS) IR infants (NS-IR, n = 74), significantly higher (47.5 vs. 20.7 microg/L, p = 0.04), and S-zinc significantly lower (9.7 vs. 10.5 micromol/L, p = 0.04). Haemoglobin concentration (Hb) did not differ between the Fe-IR and NS-IR groups. Change in weight-for-age z-score (WAZ) from 6 to 12 months and mean WAZ at 12 months was lower in the Fe-IR group compared to the NS-IR group (-1.45 vs. -1.03, p < 0.001 and -1.97 vs. -1.60, p < 0.001, respectively). There was no difference in morbidity between groups. Iron supplementation of non-iron-replete infants increased Hb and S-ferritin, but did not affect S-zinc or anthropometrical indices.'] Is iron supplementation of iron-replete Indonesian infants associated with reduced weight-for-age?