We studied the diet of the Rusty-margined Guan (Penelope supereiliaris), from March 1999 to October 2000, in an altitudinal forest fragment in southeastern Brazil, located in the Parque Municipal do Itapetinga, in Atibaia, SP We studied habitat use for feeding, strata occupied for foraging, diet seasonality and morphological characteristics of consumed fruits. We collected 223 fecal samples and recorded 25 feeding-bouts, mostly in the forest interior, and between 5.1 and 10 m high. The fruit diet was composed of 52 plant species, beyond leaves and flowers. Myrtaceae, Rubiaceae and Solanaceae were the family most represented in the fecal samples. Fruit consumption presented no seasonality in the study area, whereas flowers and leaves were consumed mainly in the dry season. Berries and drupes appeared more frequently in the diet. Rust-margined Guans are large-bodied generalist frugivores that can act as important seed dispersers in forest fragments with different degrees of degradation in the southeastern Brazil.173373382