Attempts were made to establish quantitative relationships among the average oxygen isotopic composition of local meteoric water, the oxygen isotopic composition of mammalian body water, and the oxygen isotopic composition of phosphate in mammal bones. These relationships, after calibration of the method on living specimens, would permit quantitative palaeoclimatological research based on the measurement of delta₁₈O(PO₄_3-) of fossil mammal bones. Data on delta₁₈O values of body water and bone phosphate from deer and of body water from wild boars strongly indicate that different specimens of the same species living under the same climatic conditions show the same fractionation effects. The delta₁₈O values of body water and bone phosphate from humans and pigs from different climatic conditions showed well defined, quantitative relationships with average delta₁₈O of local meteoric water. In contrast, data on cattle from different areas showed no relationship between the delta₁₈O of their body water and that of the local meteoric water. Moreover, the isotope values were widely scattered even in specimew from the same area. This scatter of values in cattle is suggested to be related to the use of different feeds (fresh or dry grass, synthetic proteins, fish flour, cereals, and corn fodder), which cause the production of widely different metabolic waters. See also AATA 19-792 for earlier study. -- AATA