The richness of flowering plants (1666 native taxa) and the originalit
y of the flora of the islands of the Gulf of Guinea are remarkable. Th
e flora of Bioko shows the highest diversity in terms of families, gen
era and species of angiosperms but, due to its proximity to the mainla
nd, the level of endemism is relatively low. The number of endemics in
the four islands has suffered a decrease in the last years, due to ta
xonomic changes. Currently, 176 endemic taxa of angiosperms are recogn
ized. Most of the endemic taxa are under-collected and information is
lacking on their biology and distribution, hence the need for inventor
y work on the flora of the islands. A measure of the similarity betwee
n the floras of the islands can be given by determination of genera in
common. The results are comparable to those obtained with Exell and W
ild's quotient of affinity and show a great similarity between neighbo
uring islands. The presence of afromontane elements and several palaeo
endemics in the mountain rain forest of the islands is notable and mak
es the study of its flora a priority for research.