An approach was developed to study the swell-shrinkage behavior of expansive soil samples in the laboratory under the action of the actual load to which the soil will be subjected in the field. The fatigue phenomenon due to cyclic drying and wetting has been under investigation, and this paper describes in detail the modified oedometer used in this investigation and the testing procedure adopted. Some typical test results are used to illustrate the fatigue behavior of undisturbed expansive soil specimens during cyclic drying and wetting.