The photoneutron cross sections of 28Si and 24Mg have been obtained with good resolution from threshold to 25 MeV and with coarser resolution to 31 MeV. Activation techniques'were used to detect the annihilation γ-quanta both singly and in coincidence. The yield curves for each reaction were analysed using the Leiss-Penfold method with bin widths of 200 keV and 100 keV for the good resolution and data, and 500 keV for the coarser data. Absolute cross sections, assigned by comparison with 12C(γ, n) 11C data, give integrated cross sections which are in good agreement with previous estimates. The cross sections for both 28Si and 24Mg show considerable fine structure which is remarkably similar. A broader “intermediate” structure is observed up to 31 MeV. The silicon and magnesium data are compared with predictions of the collective correlations model and the random phase approximation model respectively, suggesting that the degree of agreement in each case depends to a large extent on the inclusion of core excitations generally, either phenomenologically or by consideration of np- nh transitions. We conclude that the extent and nature of the dipole excitations do not differ markedly between the two nucleides in spite of apparent differences in the interpretation of the low-energy collective core spectra.