A study was undertaken to determine the extent to which DNA hyperploidy is a sensitive and specific marker for biological response to etiological factors for bladder cancer and whether the absolute nuclear fluorescence intensity (ANFI) methodology is a valid, relatively noninvasive means by which to identify DNA hyperploidy. Individuals in a 1385 member cohort were identified of their potentially high risk for bladder cancer due to their exposures to aromatic amines, primarily 2-naphthylamine (91598), and invited to participate in a screening program. Test results were provided for the 504 subjects who had ANFI urine cytology. When the population was classified by occupational exposure to aromatic amines, based on job category, the rates of positive ANFI results were 21.6 percent of the 74 exposed individuals and 3.5 percent of the 430 unexposed workers. For all ages the response was greater in the exposed group than in the unexposed group. The association between a positive response and age was significant for the unexposed group, but not for the exposed group. The rates of ANFI positive results were 7.7 percent in Blacks and 3.7 percent in Whites. None of the 26 women, all of whom were unexposed, was ANFI positive, compared with 31 of the 478 men. The prevalence of the marker was greatest for exposed workers who smoked, 23 percent, and lowest for those who had no exposure and who had not smoked, 2 percent. The authors conclude that DNA hyperploidy can serve as a marker for identifying workers who are at increased risk in occupational groups exposed to bladder carcinogens.