This study was carried out to obtain the bioavailability of cadmium in a latosol increased of a single dose of sewage sludge. Representative samples of Bw horizon of a latosol, from Duque de Caxias city - RJ, and sewage sludge from ETE Ilha do Governador, in Rio de Janeiro city were collected. These materials were characterized due to its chemical, physical and mineralogical characteristics. Latter on, the samples were mixed together and bioavailability tests were accomplished. The results show that cadmium became bioavailable in the solution in the first hour of assay. After this interval the concentration of the available metal in solution it diminished, occurring stabilization in the subsequent hours of collection.