The authors studied the cytological and cytophotometrical aspects in imprints from freshly surgically removed thyroids with the following diseases: nodular goiter, Graves' disease, lymphofibrous chronic thyroiditis, folliculo-papillary cancer, medullary carcinoma and undifferentiated carcinoma. In all the cases the cytological aspects were confirmed by the histopathological diagnosis in paraffin sections. The dextrodeviation and the plurimodal irregular aspects of nucleic acid content and nuclear volumes histograms were in agreement with the cytological features. In addition the linear regression analysis disclosed a diminished correlation between nuclear volumes and the content of nucleic acids paralleling the cellular dedifferentiation.