Nearly half of all primate species are now in danger of becoming extinct, new research shows.
The research found that primates, such as apes, monkeys and lemurs, need to be looked after urgently.
Lots of them are in danger of dying out because some are hunted for food and the tropical forests where they live are being destroyed.
One expert said: "We have the resources to address this crisis, but so far we have failed to act."
The experts from Conservation International have written a list of the top 25 most endangered primates.
The list includes five species from Madagascar, six from Africa, 11 from Asia and three from Central and South America.
This greater bamboo lemur is one of only four in its group in Madagascar
48% of the world's 634 primate species are classified as threatened with extinction.
Dr Christoph Schwitzer who helped put the report together said: "Support and action to help save these species is vital if we are to avoid losing these wonderful animals forever."
But it's not all bad news. The experts said that because of 30 years of conservation work, two of the species have been downgraded from 'critically endangered' to 'endangered'.