  Observations of the stellar and gaseous components in disc galaxies often
reveal asymmetries in the morphological and kinematic distribution. However,
the origin of this effect is not well known to date, and quantitative studies
are rare. Here, we present the first statistical investigation of a sample of
76 HI discs using the WHISP survey. We perform a Fourier analysis to study the
morphological lopsidedness. This allows to trace the degree of asymmetry with
radius. We further investigate the dependence on, e.g., the morphological type
and the environment.
