The (13)C shieldings and (13)C-(199)Hg coupling constants of fourteen phenyl- and seven alkyl- and alkenyl-mercury compounds have been obtained. Substituent effects on the (13)C shieldings are similar to those in nonmercurated phenyl compounds, with a similar relationship between (13)C shieldings and Hammett alpha + values, of para substituents. For phenylmercuric salts of carboxylic acids, the shieldings are insensitive to the particular anion. Trends in (13)C shieldings for a given compound type parallel (199)Hg shielding trends. Directly-bonded (13)C-(199)Hg coupling constants range from 1186 to 3196 Hz, two-bond coupling constants from 72 to 126 Hz and three-bond coupling constants from 101 to 221 Hz in the phenylmercury compounds. An alteration in the magnitude of J(CHg) with the number of intervening bonds is apparent. The dihedral angle dependence of 3J(CHg) in 2-norbornylmercury compounds is confirmed. No correlation was observed between the directly-bonded carbon-mercury coupling constant 1J(CHg) and the shielding of the mercury-bonded carbon, but this coupling increases significantly with increases in the (199)Hg shielding.