The objective of this study was undertaken to evaluate the factors affecting residual lesion in women withadenocarcinoma in situ (AIS) on cervical conization specimens. The medical records of women with AIS whohad no associated invasive carcinoma after cervical conization and underwent subsequent hysterectomy atChiang Mai University Hospital were reviewed. During March 1998 and March 2006, 45 women were includedfor analysis. The mean age was 45.2 years (range, 30-66 years). Thirteen (28.9%) women presented with AIS onPap smear. Thirty (66.7%) underwent loop electrosurgical excision procedure and the remaining 15 (33.3%)underwent cold-knife conization. Twenty (44.4%) women had mixed lesions of AIS and squamous intraepitheliallesion on cervical specimens. Surgical cone margins were clear in 25 (55.6%) women. Eighteen (40%) and two(4.4%) women had involved and non-evaluable cone margins, respectively. Residual lesion was noted in 14(31.1%) hysterectomy specimens. There was no residual lesion in women with clear cone margins while 72%and 50% of women with involved and non-evaluable cone margins, had residual lesion, respectively. Thesedifferences were statistically significant (P<0.001). No significant association between the ECC results and theresidual lesion was noted (P=0.29). In conclusion, approximately one-third of women with AIS on cervicalconization have residual lesion on subsequent hysterectomy specimens. Only cone margin status is a significantpredictor for residual lesion.