A description is made of the application of image analysis to quantitative deoxyribonucleic acid (DNA) determinations in a variety of cells. Optical density of the video signal from Feulgen-stained material was integrated across the area of the nucleus and values obtained related to values derived from known diploid cells. Analysis was performed on three classes of material: (1) biological material with known haploid, diploid and tetraploid nuclear DNA (standards), (2) metaplasias of the bronchial epithelium and (3) bronchogenic carcinomas. Results obtained with image analysis corresponded with expected data for the biologic standards and with microspectrophotometric data obtained for metaplasia and epidermoid carcinoma of the bronchial system. Application of this and other quantitative methods to cancer screening and biology is discussed.