The blood iron, vitamin B-12, and folate status of the 1985 birth cohort of Dutch infants aged 10.1-20.4 mo fed macrobiotic diets (n = 50) and matched omnivorous control infants (n = 57) was measured. Fe deficiency (combination of Hb less than 120 g/L, ferritin less than 12 micrograms/L, and FEP greater than 1.77 mumol/L) was observed in 15% of the macrobiotic group but not in the control group (p = 0.003). Plasma vitamin B-12 concentrations in the macrobiotic group were far below those of the control group (geometrical mean: 149 and 404 pmol/L, respectively, p less than 0.001). Plasma folate concentrations were higher in the macrobiotic group (31.6 +/- 11.7 nmol/L) than in the control group (21.1 +/- 8.8 nmol/L, p less than 0.001). In the macrobiotic group mean corpuscular volume, mean corpuscular hemoglobin mass, and mean corpuscular hemoglobin concentration were higher and hematocrit and red blood cells were lower (all p less than 0.05) than in the control group. It is advised to incorporate regular servings of animal foods into the macrobiotic diet to obtain an adequate amount of vitamin B-12.