The microstructure and tensile properties of magnesium-rare earth alloys, containing yttrium, gadolinium, or dysprosium have been investigated. The Gd-containing alloy has superior tensile properties to the alloys containing Dy or Y. Differences have been noted between the alloys in terms of precipitation reaction kinetics and precipitate volume fractions. The observed tensile behaviour has been related to the volume fraction and composition of precipitates. Gadolinium additions have been shown to produce a higher volume fraction of the beta(1) and beta phases and more rapid precipitation of beta" and beta' phases, which result in a higher tensile strength at all stages of ageing.