Short trunk dwarfism involving skeletal anomalies of vertebrae and ribs have been reported under various names. Both dominant and recessive and severe and mild conditions are found. We report on a patient without a severe handicap by age 3 years despite severe involvement of the thorax at birth, suggesting that a more complete classification of such anomalies is needed for counseling. We have used an objective method to classify 39 informative patients from the literature, 35 said to have a recessive disease and four a dominant one. Two patients with the costovertebral segmentation defect with mesomelia (COVESDEM) syndrome were added for comparison with our patient. The results of cluster analysis show that there are three phenotypic groups of patients. Cluster 1 contains 19 patients with a severe form of spondylothoracic dysplasia; cluster 2 includes patients with a mild autosomal recessive and a dominant type; cluster 3 groups the two sibs with the COVESDEM syndrome and our patient. One must be cautious in advising families of the prognosis for a child with severe structural chest deformity since it may not be severe from a functional point of view. More data are needed for complete discrimination between the mild autosomal recessive and dominant forms.