The dissection of 159 adult female Vipera aspis from Western France allowed the study of the evolution of fat bodies, ovaries and eggs during the sexual cycle. The latter is frequently biennial, sometimes triennial and only exceptionally annual. Vitellogenesis in reproductive females is essentially vernal and accompanied by a decrease in the relative mass of the fat bodies. This decrease is slow during the gestation period, when females eat little or not at all and use other reserves, including the liver. Participation of the kidneys is weak or absent. The fat bodies are reconstituted during periods of food intake; this requires one or two years, according to the duration of the potential feeding periods and feeding opportunities. Individual variation is important for all parameters including reproductive effort and available resources. Problems in evaluating reproductive effort and in comparing the relative clutch masses between viviparous and oviparous species are discussed.