Ethanol is a classic teratogen capable of inducing a wide range of developmental abnormalities. Studies in animal models suggest that differences in timing and dosage underlie this variability, with three particularly important developmental periods: preconception, preimplantation, and gastrulation. These periods of teratogenesis correlate with peak periods of epigenetic reprogramming which, together with the evidence that ethanol interferes with one-carbon metabolism, DNA methylation, histone modifications, and noncoding RNA, suggests an important role for epigenetic mechanisms in the etiology of fetal alcohol spectrum disorders (FASDs). In addition to a number of testable hypotheses, an epigenetic model suggests that the concept of a "fetal alcohol spectrum" should be expanded to include "preconceptional effects." This proposal has important public health implications, highlighting the urgency of research into the epigenetic basis of FASDs.