78 benign and malign, formalin-fixed bone or bone-associated tumors of different origin were prepared for image-cytophotometric measuring with a new method of preparing. The DNA-content of the tumors and the so resulting malignancy-grade were determined and compared with the corresponding measurements of unprepared fresh tumors respectively paraffin-embedded tissue sections. Regarding the comparison of the fresh material with the formalin-fixed material, no significant difference (p < or = 0.01) of the data could be found. There was also no significant difference (p < or = 0.01) concerning the comparison of the data obtained from the formalin-fixed material and the data from the tissue sections. The criterium aneuploidy showed a sensitivity of 86% and a specificity of 100% in regards to identifying a malignant tumor, irrespective of the preparation method. A strong correlation could be found (p < 0.001) between the DNA-malignancy grade and the survival rate of the patients.