Knowledge of the extent of vitamin A (VA) deficiency (D) is critical for identifying high-risk populations and mobilizing resources for prevention. Yet, all estimates are necessarily imperfect, often based on assumptions in the absence of data. In 1995, the World Health Organization estimated 254 million children to be VA-deficient and 2.8 million to have xerophthalmia. Subsequently, estimates were changed to 75–140 million and 3.3 million, respectively. Although both sets are consistent with a problem of enormous magnitude, the discrepancies also created uncertainty. The present analysis indicates there are ~127 million and 4.4 million preschool children with VAD (serum retinol < 0.70 µmol/L or displaying abnormal impression cytology) and xerophthalmia, respectively. More than 7.2 million pregnant women in the developing world are VA-deficient (serum or breast-milk vitamin A concentrations < 0.70 µmol/L), and another 13.5 million have low VA status (0.70–1.05 µmol/L); >6 million women develop night blindness (XN) during pregnancy annually. Roughly 45% of VA-deficient and xerophthalmic children and pregnant women with low-to-deficient VA status live in South and Southeast Asia. These regions harbor >60% of all cases of maternal XN, three fourths of whom seem to live in India. Africa accounts for 25–35% of the global cases of child and maternal VAD; about 10% of all deficient persons live in the eastern Mediterranean region, 5–15% live in the Western Pacific and ~5% live in the Region of the Americas. VA prophylaxis seems to be preventing the number of deficient preschool children from increasing while probably reducing rates of blindness and mortality. Greater effort is needed to assess and prevent VAD and its disorders, particularly among pregnant and lactating women.