Anemia is still the major nutritional problem among pregnant women in Southeast Asia. The objective of this study was to measure hemoglobin status and reduction of underweight in a group of pregnant women who received iron-fortified or nonfortified milk, and another group who received iron supplements (tablets) or placebo. The 44 women in the iron-fortified milk group received 15 mg of iron per day per 400 ml of milk, and 41 women received placebo. The 40 women in the iron supplement group received 60 mg of iron per day, and 43 women received nonfortified milk. During this intervention trial, all women were supervised from the 14th to the 18th week of gestation until delivery. Blood was sampled at 0, 5, 10, and 16 weeks of intervention. After the 16th week of intervention, the changes in hemoglobin (deltaHb) concentrations in both treatment groups (the iron-fortified milk and the iron tablet groups) were not significantly different (deltaHb: -0.5+/-0.9 and -0.3+/-0.9 g/L, respectively), but the changes were significantly greater in the nonfortified milk and placebo groups (deltaHb: -1.2+/-0.9 and -1.1+/-0.8 g/L, respectively; p < .01). The change in transferrin saturation (deltaTS) in the iron-fortified milk group (deltaTS: 3.4+/-12.9%) was greater than that in the placebo and nonfortified milk groups (deltaTS: -10.1+/-9.8% and -11.6+/-10.7 %, respectively) (p < .01). The weight gain of the subjects during intervention did not differ significantly in the fortified and nonfortified milk groups (delta weight: 5.0+/-2.0 and 5.8+/-2.1 kg, respectively), but was higher than in the iron tablet group (delta weight: 4.6+/-3.1 kg; p < .05) and the placebo group (delta weight: 3.8+/-2.5 kg; p < .001). Iron supplementation and fortification were seen to be effective in promoting weight gain in pregnant Vietnamese women. For women who are underweight, the administration of iron-fortified milk has additional benefits to those of supplementation, most likely due to additional energy and nutrient inputs.