₁₃C/₁₂C and ₁₈O/₁₆O ratios have been measured for 62 samples of the mineral malachite, taken from the patinas of ancient bronze objects (from Britain, Italy, Libya and China), in order to investigate any possible relationship which may exist between the isotope ratios and the burial conditions of the objects. The results indicate that the isotope ratios are controlled by complex factors related to the climate, vegetation and soil type at the burial site. It is suggested that the technique might be used, given favorable circumstances, in the characterization of patinas and as a possible aid in the detection of synthetic patination.