OBJECTIVES: To assess cervical shortening after loop excision of the transformation zone (LETZ), and confirm the validity of ultrasound measurement of cervical length. METHODS: Subjects (n = 29) were patients at the colposcopy clinic of Beth Israel Hospital who underwent vaginal ultrasound measurement of cervical length before and after LETZ. The pathologic specimen was measured by ruler. Mean cervical length (+/- S.D.), mean percentage (+/- S.D.) of cervical length removed, and correlation (r) between ultrasound and pathology specimen measurement were determined. RESULTS: Mean (+/- S.D.) cervical length measurements prior to LETZ were 3.2 +/- 0.9 cm and after LETZ were 2.6 +/- 0.9 cm, with a difference of 0.7 +/- 0.4 cm. The pathologic specimen (mean +/- S.D.) was 0.6 +/- 0.3 cm. The correlation between ultrasound and pathology measurement was r = 0.9 (p = 0.0001). Mean (+/- S.D.) cervical length was shortened by 22 +/- 12%. CONCLUSIONS: There is excellent correlation between ultrasound and ruler measurement of the cervix. There is significant cervical length shortening after LETZ, but further study is needed to see whether this persists or leads to pregnancy complications.