Conservationists have gone to the country -- the only location in the world where lemurs are found in the wild -- to assess the animals' situation.
More than 90 percent of the 103 species in the island nation should be on the Red List of Threatened Species, they said.
The Primate Specialist Group of the International Union for the Conservation of Nature reported 23 lemur species qualify as Critically Endangered, the highest class of threat.
Since a coup in 2009, conservation groups have repeatedly found evidence of illegal logging in Madagascar, and hunting of lemurs has emerged as a new threat.
Experts have expressed concern at the ongoing deforestation and say hunting of lemurs is at levels not seen before.
"Several national parks have been invaded, but of greater concern is the breakdown in control and enforcement," Russ Mittermeier, chairman of the specialist group and president of Conservation International, told BBC News.
"There's just no government enforcement capacity, so forests are being invaded for timber, and inevitably that brings hunting as well."