Women in the fertile age are target group for some functional food addressed to improve Iron (Fe) nutritional status since they are prone to suffer Fe marginal deficiency. In Argentina and other MERCOSUR countries people drinks mate, a Yerba Mate (Ilex Paraguariensis) (YM) infusion which contains 12 mg Fe/100g dw of low bioavailability (BA). We are presenting results of a first step in the biochemical assessment of the effectiveness of a YM with technologically improved Fe bioavailability (BA+). Voluntary healthy women 25–47 years old (n=50) were instructed to drink mate twice daily according the traditional use; half of then received BA+ at blind. Blood samples were obtained at cero time (To) and monthly during 6 m. Hematocrit (Ht) and Hemoglobin (Hb) were determined. At To, Ht and Hb were 38.1±2,8 and 12,6±0,9 respectively. In those women who have complete 180 days, significant changes were found in Ht and Hb regarding To in the B+ group (Durbin Watson p< 0,0001) whereas control group remains constant. In BA+, deltas (Δ) intersampling fit, as a function of time (x), equations with positive slope being: ΔHt=0,037x – 0,069 and ΔHb=0,0044x – 0,0044. Results of changes in traditional hematological values support effectiveness of the YM with increased BA. However, to confirm this conclusion, indicators of Iron stores are in progress. 2. MS Thesis. Fellow from Molinos Río de La Plata. 3. PIP N° 02306.