Recent research suggests that the endogenous cannabinoids (“endocannabinoids”) and their cannabinoid receptors have a major influence during pre- and postnatal development. First, high levels of the endocannaboid anandamide and cannabinoid receptors are present in the preimplantation embryo and in the uterus, while a temporary reduction of anandamide levels is essential for embryonal implantation. In women accordingly, an inverse association has been reported between fatty acid amide hydrolase (the anandamide degrading enzyme) in human lymphocytes and miscarriage. Second, CB 1 receptors display a transient presence in white matter areas of the pre- and postnatal nervous system, suggesting a role for CB 1 receptors in brain development. Third, endocannabinoids have been detected in maternal milk and activation of CB 1 receptors appears to be critical for milk sucking by newborn mice, apparently activating oral–motor musculature. Fourth, anandamide has neuroprotectant properties in the developing postnatal brain. Finally, prenatal exposure to the active constituent of marihuana (Δ9-tetrahydrocannabinol) or to anandamide affects prefrontal cortical functions, memory and motor and addictive behaviors, suggesting a role for the endocannabinoid CB 1 receptor system in the brain structures which control these functions. Further observations suggest that children may be less prone to psychoactive side effects of Δ9-tetrahydrocannabinol or endocannabinoids than adults. The medical implications of these novel developments are far reaching and suggest a promising future for cannabinoids in pediatric medicine for conditions including “non-organic failure-to-thrive” and cystic fibrosis.