Key PointsQuestionIs there an association between Agent Orange exposure and risk of bladder cancer and/or aggressiveness of bladder cancer?FindingsIn this cohort study of more than 2.5 million male Vietnam veterans, there was a modestly increased risk of bladder cancer—but not aggressiveness of bladder cancer—among veterans exposed to Agent Orange. Exposure to Agent Orange was associated with a significantly increased risk of bladder cancer, although the association was very slight (hazard ratio, 1.04; 95% CI, 1.02-1.06).MeaningThese findings suggest an association between exposure to Agent Orange and bladder cancer, although the clinical relevance of this was unclear.