Mandibular osteomyelitis in free-ranging cervids is a rare, but eventually fatal, disease. We examined 41,895 defleshed mandibles of roe deer collected throughout Slovenia in 2007. Mandibles from 14,679 fawns had no signs of osteomyelitis, and were excluded from further analysis. Of the remaining 27,216 specimens, chronic osteomyelitis (‘‘lumpy jaw'') was found in 113 mandibles (4.2%; 7.0% of adults). The majority of cases were observed from the Mediterranean and subalpine regions, near larger cities and thermal power plants. There was no statistically significant correlation between severity of the mandibular osteomyelitis and body weight. Females were more frequently affected than males. Coarse and abrasive food, and to some extent dental fluorosis, are the most probable triggers for development of lesions.