Intrauterine ultrasonography was performed using miniature probes and high-frequency ultrasound to examine the possible clinical applications of this technique to gynecology. There were 44 women in the study population (age 19-76; ten with a normal uterus, nine fibromyoma, 15 endometrial cancer, ten cervical cancer). The probe was easily introduced into the endometrial cavity in 36 subjects (81.8%). No notable complications were encountered. In subjects with a normal uterus, the endometrium in the secretory phase showed a clearly demarcated hyperechoic area, and higher resolution was obtained than with transvaginal scanning. In patients with fibromyomas, myoma nodules were not clearly visualized because of the attenuation of ultrasound. Myometrial invasion of endometrial cancer was estimated correctly in ten of the 11 patients in which the lesion was visualized. In the subjects with cervical cancer, intracervical scanning was completed in only five cases, and an endocervical lesion was identified in three cases. Intrauterine ultrasonography with a high-frequency miniature probe may be a useful tool, especially in the preoperative evaluation of endometrial cancer and possibly in infertility practice. However, this modality does not appear to be satisfactory for cervical lesions.