Several parameters that characterize a population arising from a single male–female pair of Oikopleura dioica Fol, 1872 (Appendicularia) were studied in our culture system. Egg volume varied by a factor of 1.4. Daily size of individuals in a population followed a Gaussian distribution, and the spread of this distribution increased with time. In a population that arose at 18 °C from 252 eggs, mortality reduced the number of individuals to 162 after 5 days. During the following 4 days, the appendicularians reached sexual maturity and died after gametes were released. The first individuals to mature were males, 115 h after fertilization. Average trunk sizes of mature animals are 942 ± 95 μm for males and 1165 ± 104 μm for females. All appendicularians released their gametes and died 215 h after fertilization. The number of eggs per female showed considerable variation, ranging between 41 and 362, with an average of 170 ± 78. Different causes for mortality during the entire life cycle are analysed.