That a positive correlation exists between egg size and egg energetic content is an assumption of empirical and theoretical studies of life-history evolution. Although assumed, this relationship lacks substantive support, particularly at the intraspecific level. To this end, we evaluated the validity of this assumption within and among clonal and bisexual females of the desert fish Poeciliopsis. As anticipated, we found generally high correlations between the two variables at all levels studied. Thus, egg volume remains a reliable and often precise indicator of maternal investment in this species.