A major initiative to reduce the impact of enteric infections on health and nutrition has been micronutrient supplementation. Measures for routine vitamin A and zinc supplementation are gaining increasing support from international agencies, including UNICEF and the WHO. The primary objective of this study is to compare the effect of 3 micronutrient supplements (vitamin A only, vitamin A and zinc, and a micronutrient mixture containing vitamins A, B, C, D, E, K, and calcium, copper, folate, iodine, iron, magnesium and zinc) on prevalent days of diarrhea in 3 groups of children (HIV-infected children, HIV-uninfected children born to HIV-infected women, and HIV-uninfected children born to women without HIV infection). The secondary objectives of the study are: (1) to describe the pathogen-specific pattern of enteric infections in both HIV-infected and uninfected children during ages 6-24 months, with a focus on infection with C. parvum and other protozoan pathogens and (2) to conduct a cost-effectiveness analysis of micronutrient supplementation in children aged 6-24 months. The tertiary objectives of the study are: (1) to assess whether either zinc alone or a micronutrient mixture containing zinc affects linear growth and body composition and (2) to determine if infection with specific enteric pathogens is associated with the development of persistent diarrhea lasting > 14 days. The proposed study will be conducted through the African Centre for Health and Population Studies located in Hlabisa Health District, in northern KwaZulu Natal (KZN), South Africa. The study is a randomized, double blind, clinical controlled trial with 3 arms in a study population of infants stratified by HIV status and the HIV status of their mothers. Study participants will include a total of 516 infants aged 4-6 months. The following evaluations will be made throughout the study: (1) blood samples, (2) stool sampling-routine (collected at 6, 12, 18, and 24 months of age), (3) stool sampling-during diarrheal episodes, and (3) lean body mass and anthropometry (assessed at 6, 12, 18, and 24 months of age). Study participants will be involved in study related procedures for up to 18 months.