An empirical treatment of 13C chemical shifts in arylcarbenium ions is presented which demonstrates that there is a systematic dependence of arene carbon chemical shifts on the electronic effects of carbenium-type substituents. The relationship is evident not only at positions formally conjugated with the carbenium center, such as the para position in benzene, but at most positions remote from the site of substitution in several arylcarbenium ion systems. The systematic dependence is demonstrated for each position in an aryl group by determining the carbon chemical shift response pattern, which is defined as the rate of change in I3C chemical shift relative to the rate of change at the para position of benzene. The response patterns are established by plotting chemical shifts for a series of arylcarbenium ions vs. the chemical shifts at the para position of the analogously substituted benzenes. Comparison of the chemical shift response patterns with MO calculations of the changes in charge distribution upon formation of an arylcarbenium ion from a neutral precursor shows a linear relationship between the slopes of the response patterns and the changes in charge density. 3 2 c s H 3 2 7 d \H 1 2