The Fandriana-Marolambo forest corridor is one of the largest (ca. 250,000 ha) and least explored tracts of unprotected forest in southeast Madagascar. Although published range maps show continuous distributions for many lemurs throughout the region, there are few data on lemur community structure in the corridor. We aimed to determine lemur community structure, with its ecological correlates (altitude, agriculture, selective logging, and hunting), in the Fandriana-Marolambo forest corridor. We surveyed 7 sites and sighted 4 nocturnal taxa (Avahi laniger, Cheirogaleus major, Lepilemur mustelinus, and Microcebus rufus) and 6 diurnal taxa (Eulemur rubriventer, E. fulvus rufus, E. f. fulvus, Propithecus diadema edwardsi, Hapalemur griseus griseus, and Varecia variegata variegata). Composition of the lemur community was broadly similar to that of nearby protected areas (Ranomafana and Mantadia National Parks). However, we sighted no Hapalemur aureus, H. simus, or Indri indri, and observed Propithecus diadema edwardsi and Varecia variegata variegata at only 1 site each. We sighted an apparent hybrid form of Eulemur fulvus fulvus and E. f. rufus that may represent a new hybrid zone for lemurs. After testing for spatial autocorrelation, lemur diversity correlates negatively with altitude and agricultural intensity. Though the Government of Madagascar is assessing the corridor as a new national park, we suggest conservation plans for local lemurs are complicated by population isolation and lack of data on minimum viable size of the proposed protected area.