Many authors have studied asbestos dissolution, in relation with physical and chemical properties and/or biological effects. Most often, the experiments have been carried out under conditions poorly related to health problems. A possible conclusion is a correlation between the reactivity of leached mineral surfaces and the cancerigenic power. In earlier works (Thomassin et al. 1977) we have studied the dissolution kinetics of chrysotile using XPS analysis of the solids, after leaching in non-stirred media by strong reagents (0.1 n oxalic acid and 6 n HCl). It appears that the two possible rate-limiting steps are: • -diffusion of Mg ++ through an external silica gel, • -chemical reaction. Complementary experiments carried out with 0.01 n HCl favor a rate mechanism involving a chemical reaction, followed by diffusion through a silica layer and a chemical reaction after some collapse or corrosion of the ordered silica gel. Using XPS, we have studied three aspects of asbestos dissolution related to biological problems: 1. 1.comparative leaching study of various asbestos minerals (chrysotile, crocidolite, amosite and anthophyllite) by 0.1 n chemical reagents from the Krebs cycle (pyruvic, citric and oxalo-acetic acids); 2. 2.study of the dissolution mechanism of chrysotile at very low concentrations of oxalic acid (10 −4 and 10 −6 n); 3. 3.study of the effects of grinding: The most soluble asbestos is chrysotile, the best of the investigated reagents being pyruvic acid, which is not so active as oxalic acid at the same concentration. At low concentrations, the dissolution of chrysotile in oxalic acid is limited to the first brucite layer; grinding of crocidolite favors significantly its dissolution. These few experiments enable us to suggest that in the human body, except in the stomach, asbestos dissolution is very low, favored by grinding and leaves a surface layer having ordered silanols groups, the high reactivity of which has been demonstrated in the case of chrysotile (pacco et al., 1976).