The aim of the study was a histomorphometric evaluation of bone marrow megakaryocytes (MK). The study was based on bone marrow histological evaluation. Morphometric evaluation was carried out with the aid of the MicroImage Olympus computer image analysis software. We evaluated the amount of megakaryocytes (MK) per 1 mm2, MK area, the nuclear-cytoplasmatic (N/C) ratio and circular deviation (CD). Bone marrow was examined in premature newborns, full-term newborns and adults. The obtained data were statistically analysed with the aid of the Statistica PL computer software. Statistically significant differences were found in MK quantity, their distribution in relation to non-haematopoietic elements of haematopoietic microenvironment of sinusoid vessels system. To a smaller extent, did the differences refer to MK area, the N/C ratio or shape.