The hypothesis put forward in this paper assumes that prehistoric and historical populations are characterised by a different than contemporary groups pattern of individual development. Developmental trajectories are in prehistoric and historical populations more homogenous and the unifying; role of non-genetic factors is more strongly expressed. 1'he research procedure is based on an analysis of growth and development processes in three mediaeval populations from the Polish territory (Cedynia, Słaboszewo, Gruczno).The aim of this paper is to describe the peculiarity of the developmental pattern characteristic of mediaeval samples. In the analysis, in order to construct the growth curves. 184 femoral and 186 tibial bones of subadults from three mediaeval cemeteries were used. Disruptions of bone growth in length by the occurrence of Harris lines and atrophy of cortical bone in 173 femora were also examined. Lt was found that in the mediaeval groups there was a decline in the level of growth caused by environmental factors. There are also differences in the rate of growth. Two ontogenetic phases may be distinguished, in which factors of external environment disturb development with the greatest severity. The first one is the period of weaning stress, and the second one is the age interval 6–12 years and above 12 years. Establishing of the bone final lenghts after adolescent growth spurt is prolonged in time and proceeds at the ex-pense of the thickness of bone cortical Layer.