The isotope effects on the 13C NMR chemical shifts and coupling constants ( 13C 1H and 13C 1H) have been determined by pulse Fourier transform 13C NMR investigation at 22·63 MHz for more than 30 common deuterated and protonated solvents. The observed isotope effects correlate with hybridization and electron withdrawal at the coupling carbon within the series of comparable compounds. In agreement with MO-theoretical calculations a linear correlation between the J CD values of CD x groups and the J CH values of the corresponding CH x groups was found. The experimentally determined J CD values show an average deviation from the calculated line J CD = (γ D/γ H)J CH = 0·154 ×J CH on the order of± 1 Hz.