This research was carried out in order to determine the concentration and the amount of micronutrients extracted by to varieties of lettuce plants during a life cycle. The lettuce plants were collected at the age of 20, 30, 40, 50, 60 and 70 days old from a commercial field and separated into new and old leaves and stems; then the concentrations of B, Cu, Fe, Mn and Zn were determined. There were differences in the nutrient concentrations between the two varieties, and the cultivar Brasil 48 has presentend the highest levels. The amount of Fe 6,800 µg, Mn 3,534 µg, Zn 4,462 µg; Clause's Aurélia: B 958 µg, Cu 165 µg, Fe 5,446 µg, Mn 1,025µg, Zn 2,425 µg.