The demography of a valuable timber tree, Prioria copaifera, was studied in undisturbed forest on Barro Colorado Island (BCI) in central Panama using data from a permanent, 50 ha census plot. All individuals above 20 mm diameter at breast height (dbh) in the plot were mapped and dbh measures taken in 1982, 1985, and 1990. Although Prioria is mainly known from swamp forest, it was abundant in the upland forest of BCI, with a mean density of 27–29 stems ha −1 of 10 mm dbh or more. Mortality rates of Prioria were 0.5 and 0.6% year −1 during the two census intervals and did not depend on dbh. Mean growth of saplings was slow, less than 1 mm year −1, but larger trees grew rapidly, at 8–16 mm year −1. Growth rates of medium and large trees were higher during 1985–1990, probably because a severe drought in 1983 increased forest-wide mortality rates and opened the forest canopy, allowing more light to penetrate the forest. During both census intervals, growth was extremely variable, ranging from 0 to 40 mm year −1 in different individuals. The range of variability changed little with size: across dbh values from 100 to 1000 mm, maximum growth rates were 20–40 mm year −1. Unlike absolute growth rates, however, relative growth declined with size, from about 5% year −1 in saplings to 1% year −1 in large trees, and was much more variable among small stems than among larger. Information about variation in growth between individuals and between census periods will be important in forest management, as it indicates how and to what extent silvicultural treatment might enhance timber production in Prioria. In addition, rapid growth of some stems suggests that plantation forestry might be productive in Prioria. Our finding that population density and performance were good in upland soils suggests that plantations of this species could be attempted in drier soils than previously thought necessary.