OBJECTIVE: To assess the impact of large loop excision of the transformation zone (LLETZ) for cervical intraepithelial neoplasia (CIN) on cervical morphology as assessed by three-dimensional ultrasound. DESIGN: Prospective observational study. SETTING: University Hospital in Dublin. POPULATION: Women with CIN who underwent an LLETZ procedure. METHODS: All 106 participants had a three-dimensional transvaginal ultrasound scan (3DTVS) performed immediately before and 6 months after LLETZ. The excised LLETZ specimen dimensions were also recorded. Blind analysis of the images was performed. The volume of the uterus and cervix was documented. MAIN OUTCOME MEASURES: The relationship between the extirpated LLETZ dimensions and subsequent cervical and uterine biometry, as assessed by 3DTVS. RESULTS: LLETZ induced a statistically significant reduction in both the length (mean, –0.46 cm; P < 0.001) and the volume (–6.12 cm; P < 0.001) of the uterus, and in the volume of the cervix (–1.60 cm; P < 0.001). The volume of the excised specimen had a significant impact on the reduction of the length of the uterus (β, –0.038; P = 0.012), the volume of the uterus (β, –0.791; P = 0.036) and the volume of the cervix (β, –0.121; P = 0.046). The circumference of the excised specimen appeared to have a significant impact on the length (β, –0.016; 95% CI, –0.028 to –0.003; P = 0.013) and volume (β, –0.413; 95% CI, –0.719 to –0.107; P = 0.009) of the uterus 6 months after LLETZ. CONCLUSIONS: The volume of tissue removed at LLETZ is related to the subsequent cervical volume, as well as the uterine length and volume, 6 months after the procedure.