The objective of this study was to assess lenticular changes in a young population years after exposure to protracted long-term low-dose-rate gamma radiation in Taiwan. A total of 41 males and 32 females who lived for several years in (60)Co-contaminated buildings and were less than 20 years old at their first ophthalmological examination in 1998 had a similar examination 4.7 +/- 0.5 years later. Lens opacities were examined by slit-lamp biomicroscopy and were scored by the Lens Opacities Classification System III (LOCS III) and a modified subclinical minor focal lens defect (FLD) system. The FLD scores for both eyes were significantly higher than those in the 1998 examinations. Increases in FLD scores compared to those for unexposed subjects occurred particularly in the anterior lens cortex. Increases in FLD scores were also significantly associated with the amount of previous protracted radiation exposure. An exposure-dependent increase in lens opacities was noted years after individuals relocated from the radiocontaminated environment, suggesting that late lenticular changes persisted and progressed in individuals with previous protracted radiation exposure.