In France, the American concept of the underclass has been used to ref
er to certain lower-class neighbor-hoods. Major currents in this socio
logical literature on both sides of the Atlantic are examined. In the
United States, sociologists agree on defining the underclass as an urb
an minority that, in addition, is kept on the fringes in certain ghett
o neighborhoods. Debate has arisen around three questions. What weight
does the economic factor carry compared with the racial one ? How do
specific cultural characteristics come into play ? How are social poli
cies and a culture of dependence related ? In France too, certain neig
hborhoods accumulate negative characteristics, but without being a mir
ror of American ghettos. They are places where mixing occurs and where
major government interventions are being made. They constitute hetero
geneous cultural and social spaces. By using four criteria (segregatio
n, integration ways of life, social policies) to examine the literatur
e, the inadequacy of the term ''ghetto'' is shown. The problems in the
se neighborhoods mainly stem from massive precariousness and stalled s
patial mobility.