Abstract: New intersectorial isotope data are presented for two calcites. Mendip calcite shows no detectable δ¹³C and δ¹⁸O differences between synchronous {213¯4} and {011¯4} sectors. Nottingham calcite shows a δ¹³C difference of 1.0‰ and a δ¹⁸O difference of 0.5‰ between synchronous {404¯1} and {0001} sectors. Data now available for 5 different calcites show the magnitude of intersectorial fractionation is variable; the effect on δ¹³C is twice that on δ¹⁸O. All five natural calcites also show erratic isotopic differences between symmetrically-equivalent synchronous sectors. Intersectorial isotopic fractionation is probably widespread but its cause and quantification require further work. Synchronous intracrystalline isotopic differences should be accommodated in the interpretation of isotopic data and should influence future sampling strategy.