Rosmarinus officinalis plants are self-compatible but automatic self-pollination is prevented by strong protandry. Flowers of R. officinalis set abundant seed when cross-pollinated by hand. Nevertheless, the seed set by self-pollination is clearly lower and similar in amount to those obtained in open-pollination. Insect-mediated geitonogamy is possible, and appears to be responsible for the lower seed set in open-pollination. Seed set by male-sterile plants indicates that gynodioecy could be considered as a strategy to increase reproductive output in R. officinalis. Two different steps can be distinguished in the halting of seed selfing: early abortion of the embryo/endosperm just after fertilisation, leading to small and empty seeds; and late abortion of the embryo, leading to empty but apparently normal seeds.