The prognostic significance for residual or recurrent disease of cervical intraepithelial neoplasia Grade III in endocervical glands by cone biopsy was examined in 341 consecutive patients diagnosed from 1979 through 1983 and followed through 1988. Treatment by hysterectomy, within 8 weeks of cone biopsy, was done in 96 patients. The only variable that could predict residual disease at hysterectomy was positive margins (P = 0.059). However, both positive margins and positive glands were (independently of one another and after the effects of length of follow-up, hospital of admission, and age at time of first diagnosis were held constant) highly significant predictors of residual or recurrent disease in the 245 women who did not undergo a hysterectomy (P = 0.000 for each). The authors therefore conclude that information concerning gland involvement on cone biopsy specimens should influence patient management.