Isotope shifts in nuclear magnetic shielding have been calculated in the molecular hydrogen system by a semiempirical procedure, which assumes that the high-frequency term varies with internuclear distance R as Rm. It has been found, through a comparison with other investigations, that the choice of m = −1.9 appears to be reasonable. If this choice is taken, then the isotope shift between HD and H2 becomes (0.047 ± 0.02) × 10−6, while the shielding constant for H2 is (26.51 ± 0.3) × 10−6.