Pedigrees of 2 291 lambs born during l97l and 1972 were employed in an estimation of the inbreeding coefficient of the S.A. Mutton Merino breed. Pedigrees were extended in 4 lines from the grand parents up to and inclusive of the sixth generation. Current as well as long term inbreeding was calculated. The frequency of parent-offspring matings was 1:55 while one out of every 26 matings was between half-sibs. No full-sib matings occurred. These closely related matings resulted in current inbreeding of 0,94%. The long term inbreeding amounted to 2,66% which was in part due to deliberate line-breeding. The total inbreeding of 3,60% over 6 generations implies a rise in inbreeding of almost 15% per century. No relationship was evident between flock size and increase in inbreeding possibly on account of the fact that inbreeding was purposely avoided in the smaller flocks.