Replicate measurements have been made of the Sr and Rb concentrations and Sr isotopic compositions of two total-meteorite samples of the Bishopville aubrite, and of the component enstatite and plagioclase from a third sample. These data provide an "internal" age for the meteorite. They apparently define an isochron whose equivalent age lies between 3·5 × 10 9 and 3·9 × 10 9 years at the 95 per cent confidence level, suggesting that this aubrite may have formed at a significantly later time than the major period of meteoritic fractionation some 4·5 to 4·6 × 10 9 years ago. Other interpretations for the apparent isochron are also discussed. Comparative data are also given for the Moore County eucrite which agree well with analyses reported elsewhere after the necessary normalization of isotopic ratios is carried out.