The kinetics of adsorption in the batch mode is frequently represented by the Lagergren model or the pseudo second-order model. We assess these models in their ability to represent adsorption by comparing them with the predictions of detailed intra-particle diffusion models and also with a variety of experimental data drawn from the literature. The conditions under which these two models may have rational physical significance are identified, but the data representation capabilities of these models are found to extend beyond these conditions. This is shown through a number of sample calculations.