Selected clinic patients were entered into a prospective longitudinal study to assess the incidence and rate of progression of lens opacities. Ninety-seven patients aged 15 to 88 years (median 63 years) were followed for two to 35 months (median 16 months). Lenses were photographed on a photo slit lamp and retroillumination cataract camera. Photographs were graded independently and then assessed in a side-by-side comparison. The incidence rate of cortical opacity was found to be 4% and for nuclear cataract between 11% and 20%. The rates of progression were 18% to 21% for cortical opacity, 14% to 16% for nuclear opacity, and 39% to 40% for posterior subcapsular opacities. These data suggest that these simple photographic means are sufficiently sensitive to detect changes in lens clarity.