Transrectal radial scan ultrasonography has been performed in 180 cases of stage Ib, IIa, or IIb uterine cervical cancer. Increases in the parametrial length, width, their product, and internal echo intensity as well as shift of the cervix to the side of more severe induration have been demonstrated, irrespective of the presence or absence of menstruation, as the clinical infiltration becomes more severe. Furthermore, concerning the presence or absence of histologic infiltration, there is a very strong possibility of a cancerous infiltration in cases of mass formation in the parametrium.