The giant bone cell tumour is a benign osteolitical tumour of spongious tissue. The evolving characters claimed the identification of the high-risk tumours for improving the prognostics. There were used samples of primitive tumours from 69 patients, paraffin included and coloured H&E and then examined with interactive digital video software. The quantitative standard measurements of giant cells (aria, perimeter and diameter), stereology (percentual volumes of cells, blood vessels and stroma) and proliferative activity assessment were made on the representative sections. The dimensions of the giant cells are higher in the Grade I and are lower in Grade II and III, with a dimensional variability. Bone giant cell tumours with mitotic rate less 1/mm2 were exclusively nonaggressive. Quantitative studies reveal the morphopathological changing specific for the grading and evolving forms of giant bone cell tumours. The stereology and mitotic activity index are essential predictive indicators and may be used in early detection of agressiveness and malignancy.