In Finland, 3 patients have been diagnosed with Nager syndrome (NS) during the last 17 years. Thus the incidence for NS in Finland is 3:1,000,000. The craniofacial structures and dental development of these patients were studied clinically and radiographically at the age of 3-4 years, and compared to age-matched controls and to the norms of the Finnish population. The striking structural finding was a severely short, retrognathic and posteriorly rotated mandible. Especially the ramus was deficient; its height was, on average, less than one-third of that of the control group. All children were tracheostomized neonatally. At the age of 3-4, the lower pharyngeal airway was still severely obstructed or completely closed. Nasopharyngeal airway was wide and the soft palate was missing in all patients. All patients had a complete deciduous dentition, but agenesis of permanent teeth (ranging from 2-10 missing teeth) was observed in each patient. Accelerated dental development was found in two subjects. Condylar ankylosis or severely limited mouth opening were observed. The present findings give new information and quantify earlier observations of craniofacial structures and dental development in NS. Analysis of facial structures suggests that if surgical intervention is needed to enable better breathing, the goal of the structural correction should be aimed at the most deficient structure, namely the ramus height. As a result of severe dentofacial deviation, a treatment process through the growth requires multidisciplinary teamwork of surgeons, pediatrists, orthodontists and prosthodontists.