The interdental and interspecific variation in the prevalence and severity of macroscopic fluorotic alterations of the permanent mandibular cheek teeth (P2–4, M1–3) was studied in 331 roe deer and 62 red deer exhibiting severe dental fluorosis. The material originated from the fluoride-polluted region of the Ore mountains and their southern foreland (Czech–German border region). Scoring of dental fluorosis was based on an ordinal measurement scale with six scores (score 0: unfluorosed, scores 1–5: increasing severity of fluorotic alterations). The observed variation in dental fluorosis both within the cheek tooth row of a species and between certain homologous teeth of roe and red deer could be related to the development of the dentition in the two species, especially the timing of tooth crown formation in relation to weaning and the subsequent period, where the animals feed upon (fluoride-contaminated) plant material. The lower prevalence (roe deer: 3%, red deer: 42%) and severity (fluorosis scores ð 2) of dental fluorosis in the M1 compared to the other permanent cheek teeth were attributed to the fact that the crown formation of this tooth takes place largely (roe deer) or to a considerable extent (red deer) prenatally and during the period of milk feeding. It is assumed that during these ontogenetic stages several mechanisms (partial placental diffusion barrier to fluoride, low fluoride content of milk, rapid clearance of fluoride from the blood resulting from a high skeletal growth rate) to some extent protect the developing teeth from increased fluoride exposure. Therefore, in both species apparently only the (late) maturation stage of M1 amelogenesis can be affected by fluoride in a way to induce visible enamel changes. The higher prevalence and severity of fluorotic lesions in the M2 of red than roe deer was related to the fact that in the former species crown formation of this tooth, like in the P2–4 and M3 of both species, takes place completely post-weaning.