The stability constants of chloro complexes of La3+ were determined in perchloric acid media by means of a solvent extraction method. Dinonyl napthalene sulfonic acid was used as one extractant, and the lanthanum concentration was measured by an UV-VIS method using xylenol orange at pH 6. The values obtained for, La, Cl are ( 1 +/- 0.2, 0.76 +/- 0.09, and, 0.67 +/- 0.15) mol(-1).dm(3) for ( 2, 3, and 4) mol, dm(-3), respectively. For beta(La,2Cl) they are ( 0.2 +/- 0.1, 0.09 +/- 0.02, and 0.1 +/- 0.03) mol(-2).dm(6) for ( 2, 3 and 4) mol.dm(-3), respectively. According to the specific ion interaction theory ( SIT), log beta(0)(La,Cl) = 1.4 +/- 0.1 and epsilon( LaCl2+, ClO4-) 0.62 +/- 0.03.