Two populations of Roupala montana Aubl. growing in a shrubland and in a forest were studied to assess the relative contribution of abortion and predispersal seed predation to the final seed set. Predispersal reproductive losses were similar to those observed in Australian and African Proteaceae. In both populations a final seed set of less than 2% was determined. Although R. montana produced conflorescences with numerous flowers (≥100), a high proportion of confructescences had few fruits (≤10) or were even barren due to flower-fruit abortion (97% in the shrubland and 96% in the forest), which represents the main constraint to seed production. Seed abortion and seed predation were of a lower magnitude than flower-fruit abortion. In the shrubland the only seed predator was a weevil, while in the forest at least two seed predators and hymenopterous parasitoids were found. Fruits with a single formed seed (the other one aborted) suffered less predation than fruits with two formed seeds.