The study comprised 14 pairs of twins. All the children were prematurely born between the 27 and the 33 weeks of pregnancy with birth weight 600-1900 g. Somatic development was assessed on the basis of the body weight, length/height measurements taken in the 6th and 12th months of the corrected age and in the 24th month of the calendar age. Body mass index was also calculated as weight in kilograms divided by the square of the height in meters. The obtained results were compared with the regional norms for children from Lodz. Moreover, in each child individual measurements and body mass index were normalized as compared to the arithmetic mean and the standard deviation for the established age norm. The percentage of children with body mass deficiency and decreased body length/height was relatively high. Individual assessment of somatic development, taking into account the normalized values enable observation of the direction of changes within the range of somatic features in individual children. Retardation of somatic development of prematurely born twins should be first of all associated with their very low birth weight. Severe complications of prematurity affect physical development of the children examined by us, especially in the first two years of life.