As a ring, a block arise from more than one finite group. The resulting conjugacy issue for defect groups is important for the group ring isomorphism problem and for understanding block theory in general. there are even indirect structural consequences for finite groups, through G. Robinson's work on the “Z-star theorem” for odd primes. A positive aswer to the defect group conjugacy problem is given here for the principal block in the case of cyclic, T.I., Sylow $p$-subgroups.