Lentil (Lens culínaris) production areas in Chile are being affected by a plant disorder, not related to microorganims, named "marea negra", "roña" or "sereno", which symptoms are blackish-brown spots on basal leaves, progressing to upper leaves and followed by defoliation. These symptoms are always related with high foliar Mn and Fe contents. The objectives of this study were to observe visual symptoms of Mn deficiency and toxicity in lentil, to stablish Mn critical deficiency and toxicity levels, and to relate Mn foliar levels with foliar concentrations of other mineral nutrients. Germinated lentil (cv. Araucana-INlA) seeds were grown in 12 Mn experimental concentrations, rang¡ ng from 0.0 to 1,000 μM, in nutrient solution. Plants were harvested six weeks after transplanting, top dry weights were recorded and leaf tissues were anal ized for Mn and other elements, in the dry ashes extracts. The only Mn deficiency visual symptom was reduced height of plants. Lighter Mn toxicity symptoms were similar to those of "marea negra" and were developed at Mn concentrations of 10 μM, in the nutrient solution, and 118 μg/g, in leaves. The Mn concentration in leaf tissues increased as Mn supply was increased. The Mn critical deficiency and toxicity levels were 17 and 420 μg/g, respectively. Foliar concentrations of K, Ca, Mg, P, Fe and Zn were reduced with the increase in supply and foliar content of Mn.