The design of a simple small-size antenna for Worldwide interoperability for Microwave Access (WiMAX) application is presented in this paper. The antenna covers the 3-5GHz WiMAX band. The proposed printed-type antenna is based on a 1.6 mm-thick FR4 epoxy substrate with dimensions W=25mm and L=40.5mm. It has a rectangular split-ring slot enclosed inside a rectangular patch. The inclusion of the split-ring slot and the U-shaped slot in the partial ground plane gives resonance at two additional frequencies. The dimensions of the patch, the ground, and the two slots are optimized to obtain these desired functional frequency ranges.