Cation exchange capacity, at natural soil pH and at pH 7,0, was determined within the profile of three Central Amazonian soils yellow Latosol, Red-yellow Podsol, low Humic Gley. The relationship between CTC and other soil characteristics (organic matter, specilfic surface, quantity and minerology of clay fraction) that cause variation in CTC were studied through regression and correlation analysis. The different values of CTC found were due principally to organic matter and the minerology of the clay fraction. Soil organic matter, was highly correlated with CTC (at pH 7.0) In the Veliow Lotosol(r = 0.998) and Red-Yellow Vodzol (r = 0.974), especially in the surface horizon, while the Low Humic Gley was correlated at the 5% level (r. 0,894), and witch CTC (at natural pH) In the Yellow Latsol (r= 0.98 and Red-Yellow Podzol (r = 0.984). The correlation between surface specificity and CTC was highly significant for the Yellow Latsol (r = 0.957) and Low Humlc Gley (r = 0.952), but only at the 5% level for the Red-Yellow Vodzol (r = 0.873). The textural class, organic matter, and principally, the minerological composition were responsible for high specific surface values in the Low Humic Gley.