Los Angeles has begun hosting the 86th annual Oscars ceremony at the Dolby Theatre on Hollywood Boulevard.
The historical drama "12 Years a Slave," the 3-D space spectacle "Gravity" and the con-artist caper "American Hustle" are vying for best picture in the night's closest contest.
"Gravity" is expected to lead the ceremony in total awards, cleaning up in technical categories like visual effects and cinematography.
Unlike the stormy hosting of Seth MacFarlane last year, Sunday's show, with host Ellen DeGeneres, has a deliberately safe vibe of cheery song-and-dance.
The nimble and amiable DeGeneres is expected to return the broadcast to more traditional territory.
In the first award of the night, Jared Leto, the former teen heartthrob who left Hollywood to become a rock star, won the best supporting actor Oscar on Sunday in his return to movies as an HIV positive transgender woman in "Dallas Buyers Club."
Lupita Nyong'o won the Oscar for best supporting actress for her depiction of hardworking slave Patsey in "12 Years a Slave."
Italian drama "The Great Beauty" won the Oscar for best foreign language film.
In the same category, "Omar," a thriller and love story by director Hany Abu-Assad, was only the third Palestinian film to be nominated for an Academy Award - the second for best picture in a foreign language.
However, most notable was that its nomination listed "Palestine" as the country of origin, the first time this has happened in the academy's history.
Mexican filmmaker Alfonso Cuaron is considered a certainty for best director for seamlessly marshalling new digital technology to render the lost-in-space drama.
Cuaron would be the first Latino to win the category.
While the global hit easily topped the other eight best-picture nominees at the box office, the lower budget, less widely seen "12 Years a Slave" is believed to have a narrow edge for the academy's top honour - best picture.
Though voters last year chose entertainment over history lesson - Ben Affleck's "Argo" over Steven Spielberg's "Lincoln" - many see Steve McQueen's brutal adaptation of Solomon Northup's memoir as a landmark film difficult to watch but impossible to overlook.
ABC, which is telecasting the ceremony, hopes the drama of the best-picture race will be enough to entice viewers.
The show last year drew an audience of 40.3 million, up from 39.3 million the year before when the silent-film ode "The Artist" won best picture.