Menstrual blood loss was measured in 80 apparently healthy women aged 15-44 years. The study showed a median menstrual blood loss of 37.1 ml per period and the range was from 5.4-169.0 ml. With an average menstrual cycle of 29 days and a mean hemoglobin content of 12.8 g/dl the average iron loss was estimated to be about 0.55 mg/day. The simultaneous effects of menstrual iron loss and dietary iron intake on the iron status of menstruating women were examined using multiple regression analysis. The parameters used to measure iron status were serum iron, transferrin saturation index (TSI), hemoglobin and mean corpuscular hemoglobin concentration (MCHC). Among these parameters, TSI was found to be the most sensitive indicator of changes in factors affecting iron balance moreover, it was found that with greater menstrual loss and decreasing iron intake, there was a marked fall in TSI. However, the decline of TSI did not reach a level at which deficiency of iron transport would have occurred. These results suggest that iron intake was enough to replenish the iron lost in menstruation. Results of statistical analysis showed that the upper limit of menstrual blood loss should be about 80 ml per period. Any loss above this level for continuously long period of time may lead to anemia. This condition is further aggravated by insufficient iron intake. The data from this study are useful in estimating the recommended dietary allowance (RDA) for iron for menstruating Filipino women. They will also serve as a basis of management of patients in medical practice in terms of evaluating risk of and treatment of iron-deficiency anemia.