The problem of Knight shifts in samarium intermetallic compounds is investigated using a density matrix perturbational approach, which takes into account the strong admixing between the J=⁵/₂ and ⁷/₂ levels of the Sm³⁺ ion. Particular attention is paid to the effects of crystal fields on the White-Van Vleck crossover temperature T_CO, and explicit expressions are given for the shifts in T_CO, induced by hexagonal and cubic crystal fields, correct to (B_n^m/kT)². It is shown that whereas quadratic crystal fields can either raise of lower T_CO, depending on the direction of the applied field B, cubic crystal fields always act so as to lower the White-Van Vleck crossover temperature. In addition, a method is suggested for the determination of both the bare conduction electron Knight shift parameter K₀ and the crystal-field coefficient B₂₀ in hexagonal compounds, which does not involve additional measurements on isostructural compounds containing lanthanum.