  The HI surface density maps for a sample of 18 galaxies in the Eridanus group
are Fourier analysed. This analysis gives the radial variation of the
lopsidedness in the HI spatial distribution. The lopsidedness is quantified by
the Fourier amplitude $A_1$ of the $m=1$ component normalized to the average
value. It is also shown that in the radial region where the stellar disc and HI
overlap, their $A_1$ coefficients are comparable. All the galaxies studied show
significant lopsidedness in HI. The mean value of $A_1$ in the inner regions of
the galaxies (1.5 - 2.5 scale lengths) is $\geq 0.2$. This value of $A_1$ is
twice the average value seen in the field galaxies. Also, the lopsidedness is
found to be smaller for late-type galaxies, this is opposite to the trend seen
in the field galaxies. These two results indicate a different physical origin
for disc lopsidedness in galaxies in a group environment compared to the field
galaxies. Further, a large fraction ($\sim$ 30%) shows a higher degree of
lopsidedness ($A_1 \geq 0.3$). It is also seen that the disk lopsidedness
increases with the radius as demonstrated in earlier studies, but over a radial
range that is two timeslarger than done in the previous studies. The average
lopsidedness of the halo potential is estimated to be $\sim 10$%, assuming that
the lopsidedness in HI disc is due to its response to the halo asymmetry.
