Two 3-year prospective studies from 1982-1984 and 1986-1988 in Tanzania identified 189 children with corneal ulceration, of whom 31 (16.4%) were due to vitamin A deficiency. In 1982-1984, vitamin A deficiency was responsible for 23.4% of corneal ulcers (25 of 107) compared with 7.3% (6 of 82) from 1986-1988 (P = 0.006). It is postulated that the decrease in corneal ulceration due to vitamin A deficiency can be attributed to improved measles immunization coverage.