13C and 1H NMR spectral data for a homologous series of tertiary arsines (R3As, where R = Me, Et, n‐Pr and Ph), aminoarsines and arsonium and aminoarsonium salts are reported and discussed. In nearly all cases, quaternization of the tertiary arsine to its corresponding arsonium or aminoarsonium salt causes a decrease in the magnitude of δc. These results are compared with those from an analogous study on the quaternization of tertiary phosphines, R3P. A discussion of the factors that affect the relative magnitudes of δc and R3As and R3P is given. Hammett‐Taft dual substituent parameter analysis was used to show that the positive charge on the arsenic in the atomatic quaternary salts is delocalized by an inductive mechanism. The 1H NMR spectra of the n‐propyl‐ and phenyl‐containing compounds are non‐first order. The δH and nJ(HH) values were determined by iterative computer analysis. Likewise, the nJ(CH) values for the phenyl carbons of [Ph3AsNH2]Cl and [Ph3AsNHMe]Cl were determined from the coupled 13C NMR spectra. Copyright © 1989 John Wiley & Sons, Ltd.