The age of onset and morphology of the earliest lesions of dyschondroplasias in pigs have not been established. Bones and growth cartilages from pigs were examined for the presence of lesions using radiological, angiomicrographical and histological techniques. Lesions were in 10 of 11 pigs at 15 days of age and 12 of 21 pigs at one day of age, indicating that the condition was congenital. The simplest and apparently earliest lesion was an area of persistent hypertrophied chondrocytes and matrix which extended from the articular-epiphyseal complex or physis into the epiphysis or metaphysis, respectively. Since the prevalence of lesions was high it was considered that the dyschondroplasia may be part of the usual growth pattern of cartilages in contemporary pigs.