Polystyrene of various molecular weights has been terminally grafted onto surface-modified silicas. Small-angle neutron scattering has been used to investigate the structure of these adsorbed layers. For grafted layers in which the polymer also physically adsorbs, there is no clear evidence of scattering from fluctuations at the highest scattering vector studied (0.7 nm(-1)). Experiments carried out where the particle scattering length density has been matched to the substrate give virtually the same volume fraction profiles as do those which are not matched. However, for a system where the polymer does not physically adsorb, it is not possible to give an absolute indication of a possible contribution from fluctuations at high and because of uncertainty in the background scattering. This problem can be overcome by fitting the data sets such that any Lorentzian contribution at high and is effectively eliminated, minimizing any anomalous scattering. The results are compared with mean-field calculations and scaling predictions for polymer adsorption. For systems where the adsorption enthalpy is unfavorable, the volume fraction profiles of the adsorbed layer show a distinct maximum, whose position depends on molecular weight and surface coverage. The root mean square thickness of the adsorbed layer in this case follows reasonably well the scaling prediction of Alexander and de Gennes. For favorable values of the adsorption enthalpy, the volume fraction profiles fall monotonically in a manner similar to that found for homopolymer adsorption.