Abstract: 3-Hydroxypyridin-4-ones of formula (I) ##STR1## in which R.sub.1 is a methyl, ethyl, 2-(.alpha.-methylpropionyloxy)ethyl or 2-pivoloyloxyethyl group and R.sub.2, R.sub.3 and R.sub.4 are each separately selected from hydrogen and methyl, ethyl, 2-(.alpha.-methylpropionyloxy)ethyl and 2-pivaloyloxyethyl groups with the provisos that (a) one only of R.sub.1 to R.sub.4 is either a 2-(.alpha.-methylpropionyloxy)ethyl group or a 2-pivaloyloxyethyl group, (b) at least one of R.sub.2 and R.sub.3 is other than hydrogen and (c) the total number of carbon atoms in R.sub.1 to R.sub.4 is no more than eleven, and physiologically acceptable salts thereof are of use in therapy, particularly in the treatment of conditions in which there is a toxic concentration of a metal, for example iron, in the body.