Juvenile oyster disease (JOD) has had severe impacts on eastern oyster, Crassostrea virginica,culture in the northeastern United States in recent years. JOD mortalities in Maine have resulted in juvenile crop losses exceeding 90%. Previous research has demonstrated an inverse relationship between oyster size and JOD-induced mortality; thus the use of genetically selected broodstock along with specific management options may help manage JOD-related mortality. The goals of this project were to determine the size specificity and temporal and spatial variability of JOD outbreaks with respect to several lines selected for fast growth. Two lines (including within line unselected controls) having undergone two generations of selection for faster growth, along with an unselected wild line, were deployed during the 1994–1995 growing seasons at two sites in the Damariscotta River, ME, an estuary historically impacted by JOD. Periodic monitoring of size (shell height and live weight) and mortality of replicate cohorts was conducted to track oyster growth and incidence of JOD-induced mortalities. Due to the asynchrony of spat deployment between the cohorts, differences among lines were not feasible to evaluate, but within two lines (Flowers G2and Milford G2), selected sublines both outgrew the within line controls and had lower rates of JOD-induced mortality. The reduced mortality in the selected sublines presumably resulted from their faster growth and hardiness thus enabling the cohort to reach a refuge size/age sooner and reduce its susceptibility to JOD.