Millimeter-scale growth rings in canine dentine of MIS 3 cave bears have been interpreted as annual growth bands produced, in part, by seasonal variation in growth rate. We present new intra-tooth stable carbon (δ 13 C) and oxygen (δ 18 O) isotope profiles in dentine hydroxyapatite of early forming permanent teeth from three famous Late Pleistocene cave bear sites from Romanian Carpathians. We measured δ 13 C and δ 18 O of the CO 3 fraction of dentine hydroxyapatite from samples covering consecutive inferred years of growth in canines. The δ 13 C values retrieved from the dentine layers-from the oldest to the newest-of the same individual, record an increase throughout immature life of bears as has been shown previously, with lower precision, using age categories. For the first time, based on δ 13 C data analysis, the weaning process in cave bears was identified. The δ 18 O values show substantial variations related, most probably, to seasonal growth of the dentine. Finally, the CO 3 of dentine apatite extracted from cave bear canines proves to be reliable for geochemical analyses, reflecting palaeoclimate conditions, physiology and behavior.