We report on measurements of the dispersion amplitude for the Mössbauer resonances in 237Np (60 keV), 182W (100 keV) and 195Pt (99 keV). For the E1 transition in 237Np a value of ξ=−(3.4+0.2) ×10−2 was found. Theoretical estimates of ξ for this case are of limited accuracy and the comparison with experimental data is inaccurate because of the considerable line broadening. Computer simulations show the influence of ξ on 237Np hyperfine spectra. For the E2 transition in 182W the dependence of the effective value of ξ on absorber thickness was studied. Extrapolations to zero thickness yield ξ=−(1.0±0.1) ×10−2 in good agreement with theoretical calculations. For 195Pt we found ξ=−(1.1±0.3) ×10−2 for the dispersion amplitude at zero absorber thickness. This is the first pure M1 transition for which a dispersion term has been observed. For all three resonances the dispersion is large enough to affect the determination of isomer shifts.