A mass spectrometric technique applicable to the study of high ionization potential elements has been used to investigate the possibility of natural processes producing variations in the isotopic composition of zinc. No significant variations were detected in the samples studied. The isotopic abundances of the mass 64, 66, 67, 68 and 70 isotopes in terrestrial zinc are estimated to be 48.6 ± 0.1, 27.90 ± 0.08, 4.10 ± 0.03, 18.8 ± 0.2 and 0.62 ± 0.01 per cent respectively. Zinc concentrations have been determined in 14 stone, 1 stony-iron and 20 iron meteorites and in a large number of terrestrial samples using isotope dilution and atomic absorption methods. The range of concentrations found in stone meteorites and terrestrial rocks is similar to that previously reported, but for the iron meteorites a slightly wider concentration range has been observed (0.026-90 ppm).