Renal transplant is performed on patients with end-stage renal disease. Gray-scale renal sonography combined with color Doppler has become the main noninvasive imaging method for evaluating a kidney transplant, as it provides information about the kidney anatomy and its vascular flow. In this article, we discuss the utility of sonography in renal transplants and describe the ultrasound findings in early and chronic graft pathology. Also, we explain new developments in ultrasound imaging with contrast media and its utility in renal transplantation, proposing that contrast-enhanced sonography be incorporated as a method to evaluate graft status because of its capability to evaluate cortical capillary blood flow.