High resolution low-energy electron diffraction measurements are reported that demonstrate the existence of semiordered islands on the clean Pd(110) surface. The islands are stable up to 1000 °C and are approximately 90 atoms long in the 001 direction. A simple model is presented that makes use of step-step interactions to generate the periodic island structure. This model predicts that ordered islands form below the roughening temperature if the step creation energy is small compared to the step-step interaction. A justification for this condition is given for the Pd(110) surface. © 1993 The American Physical Society.