AbstractThe incredible pollination mechanisms displayed by orchid flowers has inspired biologists over the centuries. Based on the intriguing flower structures, the relationship among orchid species and their pollinators has been frequently regarded as very specialised.Given that visits on flowers pollinated by oil‐collecting bees are regularly rare, and in Oncidiinae the flowers frequently attractexclusively species that act as effective pollinators, the comparative reproductive biology and pollinator specificity of two sympatricGomesa(G. varicosaandG. montana; Oncidiinae) were analysedbased on records of floral morphology, production of floral rewards, pollinators and pollination mechanisms. Furthermore, experimental pollinations were carried out in order to examine the breeding systems.The results have show that in the studied population, bothGomesaare visited by several bee species, but these orchids present a specific pollination system.Pollinaria are deposited on the head of Centridini (G. varicosaandG. montana) and Epicharitini (G. varicosa) bees when landed on the central callus of the labellumto collect lipoidal substances produced by glandular elaiophores on lateral lobes of the labellum. Both species are dependent on a biotic pollen vector to set fruits.Gomesamontanais completely self‐incompatible, whileG. varicosais partially self‐compatible.Our results indicate that although the occurrence of self‐sterile species seems to be common in Oncidiinae, in partially self‐incompatible species, as is the case ofG. varicosa, self‐compatibility has been considered as an important factor favouring reproductive assurance in populations with low visitation frequencies, despite occurrence of inbreeding depression.