Some physiological, phytopathological and biotic factors affecting development, production and survival of rubber seed under field conditions were studied. Incidence of parthenocarpy, per se, was very low in all clones examined and could not account for the common absence of endosperm in seeds collected from the forest floor. Four genera of fungi associated with the flowering stage were implicated in subsequent floral abortion. Two of them, Phytophthora and Helminthosporium also interferred with post-anthesis stages of development, causing rotting of seed parts and pericarp tissues. Seed survival on the forest floor was affected seriously by various agents including insects, arachnids, nematodes, molluscs and mammals. The effect of these factors on large-scale commercial seed production is discussed.