A field experiment was established on Alonso soil (Oxic Dystrudept) to evaluate soil extractable aluminum. Plots included full sunlight coffee, high density shade coffee, and low density shade coffee. Soil samples were collected at 0-20 and 20-40 cm depths. Soil pH at 0-20 cm was 5.12 for full sunlight, 4.47 for high density shade, and 4.83 for low density shade. At 20-40 cm depth soil pH was 4.64, 4.57, and 4.66, for the same treatments, respectively. Organic matter content at 0-20 cm depth was 2.77 at full sunlight, 2.89 at high density shade, and 3.58 at low density shade. At 20-40 cm depth was 2.02, 2.04, and 2.63, respectively. Four Al³⁺ extractants were evaluated: 0.2M NH₄Cl, 1M KCl, 0.33M LaCl₃, and 0.5M CuCl₂. In the full sunlight plot, at 0-20 cm depth, 0.2M NH₄Cl extracted 5.97 cmol_c kg^-1 of Al³⁺, 1M KCl extracted 7.60 cmol_c kg^-1, 0.33M LaCl₃ extracted 7.22 cmol_c kg^-1 and 0.5M CuCl₂ extracted 9.33 cmol_c kg^-1. In the high density shade, extractable Al³⁺ were 6.47 cmol_c kg^-1, 7.99 cmol_c kg^-1, 8.18 cmol_c kg^-1, and 9.96 cmol_c kg^-1, for the same treatments, respectively. Extractable Al³⁺ in the low density shade was significantly lower than in the other plots. The 0.2M NH₄Cl solution extracted 1.82 cmol_c kg^-1, 1M KCl extracted 2.52 cmol_c kg^-1, 0.33M LaCl₃ extracted 2.28 cmol_c kg^-1, and 0.5M CuCl₂ extracted 6.73 cmol_c kg^-1. Extractable Al³⁺ at 20-40 cm showed higher values with all extractants. Lower amounts of Al³⁺ were extracted from the low shade density plot, which contained the higher organic matter content.