The effect Coffea arabica and Pithecellobium carbonarium leaf litter on exchangeable Al3+ content of Alonso soil (Oxic Dystrudepts) was studied. Four treatments were evaluated: 1) No leaf litter (Check); 2) three percent Coffea arabica leaf litter; 3) three percent Pithecellobium carbonarium leaf litter; and 4) three percent of a 1:1 Coffea Arabica:Pithecellobium carbonarium leaf litter mixture. Six grams of leaf litter were mixed with 200 g of soil collected at 0-20 and 20-40 cm depths. The soil was moist with 60 ml of distilled water, placed on glass jars and incubated at room temperature. Each treatment was replicated four times. After five months of incubation, the pH of the 0-20 cm soil samples, treated with Pithecellobium leaf litter was 3.97,for the 1:1 leaf litter mixture was 4.18 and for the coffee leaf litter and the check samples was 4.55. Exchangeable Al3+ decreased from 0.64 in the control treatment to 0.07 cmolc kg-1 in the coffee leaf litter treatment. Pithecellobium leaf litter decreased exchangeable Al3+ to 0.46 and the 1:1 mixture to 0.26 cmolc kg-1. A similar effect was observed on the 20-40 cm depth samples. The highest pH (4.29) was observed on coffee litter treated samples, the check showed a pH of 4.00, the 1:1 leaf litter showed a pH of 3.94 and the Pithecellobium leaf litter showed a pH of 3.90. The highest soil exchangeable Al3+ (1.43 cmolc kg-1) was observed on the check treatment, followed by the Pithecellobium leaf litter with 1.29 cmolc kg-1, the 1:1 mixture with 0.59 cmolc kg-1 and the coffee leaf litter with 0.31 cmolc kg-1. The fact that no significant reduction in pH was observed with the addition of coffee leaf litter indicates that other mechanisms, besides pH, are involved in the reduction of exchangeable Al3+.