The Frenchy romantic café tune that plink-plinks at the beginning and end of XX/XY is no accident: A naturalistic, Gallic storytelling style influences writer/director Austin Chick's restlessly honest American indie about men, women, and the chromosomal differences that shape male and female attitudes toward relationships. Look closely and you can detect the DNA of Erick Zonca's ''The Dreamlife of Angels'' in the cellular structure of this intimate sketch about longing and ambivalence: Sarah Lawrence students Sam-as-in-Samantha (Maya Stange) and Thea (Kathleen Robertson) meet Coles (Mark Ruffalo) at a party in the early 1990s and fall into a regularly mutating ménage à deux and trois that runs out of fun when Sam can no longer keep things light and Coles can't deal with anything heavy. (Thea, meanwhile, just likes to make mischief.) Ten years later, when Coles runs into Sam in Manhattan, the old itch to have the girl he couldn't stick with in the first place kicks in again, ignited by Sam's own unextinguished torch for her ex. Although he now lives with a brisk, blond girlfriend (''24'''s Petra Wright), Coles dithers, nearly ruining everything, while the women around him buckle, flail, and rage in his emotional absence.
Emotional presence and a sophisticated understanding of commitment-phobia (as something other than a comedic punchline or an excuse for sex scenes) distinguishes this intense, contained drama, as does the unforced, sensual, and sensitive cinematography of Uta Briesewitz (HBO's ''The Wire''). Ultimately, though, this is an actors' film, crucially dependent on the skill of the players to make a handful of difficult characters sympathetic even when unlikable. And the players win -- the cast radiates integrity and intelligence, none more so than the superb Ruffalo, who shot ''XX/XY'' before the wide release of ''You Can Count on Me'' announced his charismatic XY factor to a larger audience.