Echolocation calls of 10 species of rhinolophid and four species of hipposiderid bats were recorded in China. Close negative relationships were found within Rhinolophidae and Hipposideridae between call frequency and ear length. Multiple regression and residual analysis were used to evaluate the influences of forearm length and ear length on call frequency and ear size. Ear length proved to be a more important morphological parameter influencing the call frequency in rhinolophids but not in hipposiderids. Ears are largely shaped by echolocation calls in both families. The influence of body size on ear size was significant in rhinolophids but not in hipposiderids, and the enlarged ears of rhinolophids correlated with the lower frequencies that rhinolophids used relative to larger body size.