  We study the nucleon-nucleon interaction in a chiral constituent quark model
by using the resonating group method, convenient for treating the interaction
between composite particles. The calculated phase shifts for the 3S1 and 1S0
channels show the presence of a strong repulsive core due to the combined
effect of the quark interchange and the spin-flavour structure of the effective
quark-quark interaction. Such a symmetry structure stems from the pseudoscalar
meson exchange between the quarks and is a consequence of the spontaneous
breaking of the chiral symmetry. We perform single and coupled channel
calculations and show the role of coupling of the $\Delta\Delta$ and hidden
color CC channels on the behaviour of the phase shifts.
