  The results on the measurements of the top-quark mass, based on the data
collected by the Tevatron experiments CDF and DO at Fermilab during Run I from
1992 to 1996, are summarized. The combination of the published results, taking
correlated uncertainties properly into account, is presented. The resulting
world average for the mass of the top quark is: $M_t = 178.0 \pm 4.3 GeV/c^2$,
where the total error of consists of a statistical part of $2.7 GeV/c^2$ and a
systematic part of $3.3 GeV/c^2$.
