The solvent extraction of the trivalent lanthanides and yttrium from nitrate media by 0.5M solutions of four different 2-bromoalkanoic acids (HA) in xylene was studied. The extraction of these metals was found to take place in a pH range about one pH unit more acidic than with the parent alkanoic acids. The order of selectivity towards the individual lanthanides and yttrium was found to depend markedly on the structure of the 2-bromoalkanoic acid. Thus, for the most sterically hindered compound used (2-bromo-2-ethylhexanoic acid) the pH0 5values decrease more or less continuously from lanthanum to lutetium, although the overall difference is quite small (pH0 5LUpH0 5LU= 0,30 pH unit). With this extractant the behaviour of yttrium most closely resembles that of the light lanthanide, neodymium. For the least sterically hindered extractant used (2-bromodecanoic acid) the pH0 5LUvalues decreased only in the interval from lanthanum to praseodymium, following which the values increase more or less continuously through to lutetium, with the overall change representing a small selectivity towards lanthanum (pH0 5LUpH0 5LU= -0.12 pH unit). With 2-bromodecanoic acid and analogous compounds of low steric hindrance (2-bromo-3-cyclohexylpropanoic and 2-bromo-3,5,5-trimethylhexanoic acids), the extraction of yttrium was found to be less than that of any of the lanthanides.