Investigating the value of a number of supravital strains for use in exfoliative cytology, the authors found cresyl blue (1% solution in distilled water), with and without Sudan III (0.3% in 70% alcohol), to be reliable and relatively long-lasting. Specimens stained with cresyl blue and Sudan III can be kept for one or two days, or for longer periods (up to 3 weeks or more) if a moist chamber is used containing filter-paper moistened with 10% formol to prevent fungal contamination. These stains are less toxic than Janus green and simpler to use than neutral red. The minimum of simple laboratory apparatus is needed.During 1960-62, 1955 specimens from 460 hospitalized patients in Beer-Yaacov, Israel, were stained with these two preparations. Cytological examination led to a diagnosis of cancer in 16% of the patients, with only 9 false diagnoses.