The purposes of this study were to evaluate the prevalence and imaging characteristics of ovarian teratomas that appear as solid masses on ultrasonography and to compare the ultrasonographic imaging features of the tumors with their pathologic findings. The ultrasonographic images of 202 ovarian teratomas were reviewed retrospectively. Solid-appearing masses were selected from among them and were evaluated in terms of internal echotexture, the presence or lack of peripheral hypoechogenicity, posterior sonic attenuation, and tumoral calcification. Seventy-six (37.6%) masses of 202 belonged to the atypical solid-appearing masses on ultrasonography. Of 76 masses, 57 (75.0%) had peripheral hypoechogenicity; 38 masses had well-defined thin hypoechoic rims, whereas 19 had poorly demarcated peripheral hypoechogenicity. Posterior sonic attenuation was evident in 18 (23.7%) masses. The presence of peripheral hypoechogenicity, which is suggestive of the fluid portion of the tumor, might be one of the characteristic findings of solid-appearing ovarian teratomas on ultrasonography.