The barrier islands of the Virginia Coast Reserve LTER site provide an opportunity to study interisland variability of dune plant communities. Our research focused on the variation in biomass and diversity of communities among islands and dune positions. Grassy dunes of young, intermediate and old age were sampled on Smith, Hog, and Parramore Islands. Above- and belowground biomass were obtained from harvest plots and roots were extracted from cores. Data were also collected on depth to groundwater and total soil nitrogen. Variation in mean aboveground biomass was evident among the islands with the highest values on Hog Island, followed by Smith. Results for belowground biomass were similar, though the highest values were on Smith Island. Parramore Island showed the lowest values for both measures. Aboveground biomass was greatest on intermediate dunes, followed by the older dunes. The young dunes, constantly disturbed by overwash, had the least. Patterns in belowground biomass were variable among the different age dunes, with significant differences on Smith Island. In general, the oldest dunes had the highest biomass and the young the least. Species richness ranged from 40 species on Smith Island to 33 species on Parramore. Among dunes, results varied from an average of 17 species on the older dunes to 10 species on the youngest. The oldest dunes had the highest levels of total soil nitrogen, followed by the intermediate and young dunes. Smith Island in particular showed significantly greater values on the old and intermediate dunes. The taller intermediate dunes had the greatest mean depth to freshwater and the young fore dunes the least. Aboveground biomass increased as depth to freshwater increased on both Hog and Smith Islands, perhaps due to partitioning of resources to shoots rather than roots. Greater soil nitrogen correlated with increased belowground biomass on Smith Island, while on Hog depth to freshwater seemed to be more important. On both islands, higher soil nitrogen correlated with increased species richness. In this study, both depth to freshwater and the availability of soil nitrogen had variable effects on above- and belowground biomass, as well as species richness, depending on the island and position on the island.