Our preliminary report presents two cases of osteogenic sarcoma examined after initial chemotherapy. In both cases histological maps with morphological effects of chemotherapy and flow cytometry of DNA content in tumour cells were made. Results of flow cytometric DNA histograms were linked with an estimation of the proliferative potential of tumours. The correlations between histological grade, proliferative potential of tumours with the morphological effects of chemotherapy were confirmed in the presented cases. Flow cytometry results were ready in a few hours after surgery, when full histopathological analysis was available in 2-4 weeks. Analysis of the two methods of estimation of osteogenic sarcoma suggests that flow cytometry may be a complementary method to histological examination and estimation of proliferating rate, especially aneuploid cell population and this information can be helpful in clinical management.