THE PUBLICATION of the monograph, S "Diagnosis of Uterine Cancer by the Vaginal Smear,":'5 numerous rep0rtsl-3~ 6, 7 , 9-12, 15-17. 20-25* 32-399 42-44 have attested to the value of the method as a preliminary or an accessory procedure in detecting carcinoma of the cervix, including thc early stage, in situ carcinoma. The employment of the method, as in a population-screening program, is demanding, however, in terms of both the time and the skill of laboratory personnel. It might be estimated, for example, that the thorough examination of every field in the slides from twenty-five patients, per day, would ideally utilize the full time of two cytologists and the consultative time of a pathologist. It is to be acknowledged, moreover, that for the present and the immediate future there is a shortage of adequately trained microscopists for performing this particular type of diagnostic work.In view of these considerations, the development of a quantitative209 27.281 30 and, ultimately, automatic scanning method28 for the preliminary screening of smears for the presence of cancer cells has been undertaken. This paper presents, as a rational basis for the meth-From the Sloan-