The classic definition of a nevus depigmentosus is a stable congenital leukoderma that may be localized, segmental, or less often, systematized. Herein we report 2 patients whose achromic nevi underwent an unusual change--the development of multiple lentigines. The lentigines ranged in size from 3 to 5 mm and the majority had an irregular outline. Although their color was darker than that of the normal surrounding skin, the most striking clinical finding was their limited distribution. The lentigines were present only within the confines of the nevus depigmentosus. They first appeared at age 3 years in 1 child and at age 1 year in the second. No new pigmented macules were noted in the older child after age 10 years and, by that time, greater than 90% of the nevus depigmentosus was "repigmented." One possible explanation would be the reversion of a mutation in 1 of the genes involved in pigmentation.