A glasshouse experiment was set up the Centro de Investigaciones de Janaro Herrera in the Peruvian Amazon to determine the effect of Pontoscolex corethrurus inoculation on litter weight loss and soil inorganic nitrogen (NH4+ and NO3-). The soils in mesocosms were covered by leaf litter from two timber trees, Cedrelinga catenaeformis, Simarouba amara and mixture of both. The experiment lasted one year, evaluating three treatments: inoculation of juvenile P. corethrurus (T1); inoculation of adult P. corethrurus (T2); and, without earthworms (T3). Four replications were used for each litter type: Cedrelinga, Simarouba, and a mixture of both. The following parameters were determined: the weight of the remaining litter, the density of juvenile and adult P. corethurus, earthworm activity based on faecal pellets, carbon and macro-nutrient concentrations in faecal pellets, and soil inorganic nitrogen. There was a higher density of adult P. corethrurus in the Simarouba litter; however, earthworm biomass was similar across treatments and litter types. The inoculation of juvenile and adult P. corethrurus considerably increased NH4+ and NO3-concentrations in the soil. This was particularly true for adult earthworms, the most effective in mineralizing nitrogen. Pontoscolex corethrurus had a positive effect on litter weight loss and Cedrelinga litter (with higher nutrient concentration) lost more weigh (91.1%) than that of Simarouba (73.3%). Thus, the addition of fast-decomposing and high-quality litter or green cover to tropical soils could increase the release of nitrogen and the soil mineralization and nitrification potentials. Copyright 2006 College of Arts and Sciences University of Puerto Rico, Mayagüez.