This investigation was undertaken to study the effects of hormones, sugars and amniotic fluid on the maturation of brush border enzymes in the human fetal intestine, at early stages of gestation. Intestinal explants from 8-13-weeks fetuses were maintained in organ culture for 3 days in the presence of the agents to be tested. The data show that the explanation of human fetal gut in a serum free culture medium elicits a significant maturation (2-4-fold increase above preculture levels) of lactase and aminopeptidase whatever the gestational stage studied and of sucrase and alkaline phosphatase at specific stages of development. To be expressed, the overall maturation needs the presence of sugar (in particular glucose) in the culture medium. The addition of dexamethasone, insulin or amniotic fluid to the medium did not further enhance brush border enzyme activities except for lactase whose levels were doubled by the dexamethasone. The present data suggest that in addition to the differences which exist among mammalian species in the timing of enzyme development, there may be a species specificity in the factors involved in fetal enzymatic maturation.