Flower, fruit, seed production, and flowering phenology (duration, intensity, moment and synchrony) were studied in the two main populations (south east Spain) of the critically endangered endemic Mediterranean plant Coincya rupestris subsp. rupestris (Cruciferae). Production of flowers and fruits (mean ± SD) ranged from 483 (± 688) to 748 (± 636), and from 317 (± 518) to 553 (± 500), respectively, between populations. In addition, the average seed production per plant was 1,607-2,798, thus concluding that fertility was not responsible for the rarity of this taxon. The fruit/flower ratio ranged from 0.60 to 0.75, showing significant inter-population differences. Flowering extended from February-March to the end of spring, with high synchrony (= 85 %). This parameter was negatively correlated with duration of the flowering period. The role of pollinator insects on reproductive success, and the effect of watering treatments and the elimination of competitors on seedling recruitment were analysed in the classical locality. The exclusion of pollinators dramatically affected fructification, reducing reproductive success from moderate values in plants exposed to insects (= 0.5) to null values in those where insects were experimentally excluded. Seedling emergence was autumnal and no influence of the factors analysed (i.e., water availability and inter-specific competition) was detected on seedling establishment. A high interannual variability in the size and survival of cohorts originated each autumn was observed. It should be emphasized that the rarity of the taxon is not due to fecundity restrictions.