A census of all plants of V. sororia 1-yr-old or older was conducted at regular intervals over an 8-yr period in a forest site in New England [USA]. Over a 2-yr period seedlings were similarly recorded, and each leaf and reproductive structure on 20 selected plants was marked and its fate recorded at weekly intervals. Calculations were made of population flux, age distribution, survivorship and life expectancy of 1-yr-old or older plants and of seedlings. Fluctuation in population size was small compared to the number of individual plants gained and lost in the population. There was a remarkably constant annual death risk, superimposed upon a seasonal cycle; May-Sept. was a period of greater mortality than the winter months when the plants were inactive. The life expectancy of a 1-yr-old plant was over 10 yr. While seedlings and adult plants exhibited a Deevey type-III mortality curve, leaves had a Deevey type-I curve. Seedling survival and production-probability are a function of plant size; the relationship may be exponential in the case of seed production. Individual plant size may be regulated by competition for environmental resources.