OBJECTIVE: To investigate the expression of HIF-1α during the postnatal development of the mandibular condyle under normal and soft consistency diet conditions.MATERIALS AND METHODS: Forty eight Wistar-Furth rats, aged 21 days, were divided into two groups, each being fed with either normal or soft consistency diet. Three animals from each group were sacrificed after 3, 7, 10 days (initial period), 14, 17 days (intermediate period), and 21, 24 and 28 days (final period) after the start of the experiment. Immediately after sacrifice, the mandible was excised surgically, fixed, demineralised and embedded in paraffin. Six µm thick sections were obtained, processed for conventional and immunohistochemical staining and observed in the optical microscope. HIF-1α expression was assessed semiquantitavely and graded separately for the nucleus stained cells and the cells stained exclusively in the cytoplasm. Differences in HIF-1α expression in the experimental groups were evaluated statistically.RESULTS: HIF-1α expression was evident in the proliferative and chondroblast layers. No differences were observed between the anterior, the intermediate and the posterior parts of the condylar cartilage. In the normal consistency diet group, nuclear HIF-1α expression increased gradually until the end of the experiment. On the contrary, in the soft diet animals, nuclear HIF-1α expression increased only at the final period of the experiment. The normal diet fed animals exhibited more intense nuclear HIF-1α expression compared to cytoplasmic expression.CONCLUSIONS: HIF-1α expression in condylar chondrocytes varies under altered conditions of diet consistency.