The products of the transmutation of mercury by fast (Li+D) neutrons were investigated. Three radioactive gold isotopes were found to be formed by the $n\ensuremath{-}p$ reactions: 65-hour ${\mathrm{Au}}^{198}$, 78-hour ${\mathrm{Au}}^{199}$, and a new unassigned electron emitter with a period of 48 min. Three radioactive platinum isotopes were observed and attributed to $n\ensuremath{-}\ensuremath{\alpha}$ reactions in mercury: 29-min. ${\mathrm{Pt}}^{199}$, 19-hour ${\mathrm{Pt}}^{197}$, and a new activity with an 80-min. half-life. The latter period was also observed in deuteron and fast neutron bombardment of platinum, but was not found in slow neutron irradiation of platinum. Radioactive mercury isotopes with 43-min., 25-hour, and 50-day periods were observed in the fast neutron irradiation of mercury. The 43-min. and 25-hour activities were also formed by bombarding platinum with $\ensuremath{\alpha}$-particles. Difficulties in the assignment of the 80-min. Pt and the 43-min. and 25-hour Hg activities are discussed.