This is an updated version of the original Cochrane review published in 2014, Issue 4. Cervical intraepithelial neoplasia (CIN) precedes the development of invasive carcinoma of the cervix. Current treatment of CIN is quite effective, but there is morbidity for the patient related to pain, bleeding, infection, cervical stenosis and premature birth in a subsequent pregnancy. Effective treatment with medications, rather than surgery, would be beneficial. To evaluate the effectiveness and safety of non-steroidal anti-inflammatory agents (NSAIDs), including cyclooxygenase-2 (COX-2) inhibitors, to induce regression and prevent the progression of CIN. Previously, we searched the Cochrane Gynaecological Cancer Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 11), MEDLINE (November, 2013) and Embase (November week 48, 2013). An updated search was performed in August 2017 for CENTRAL (2017, Issue 8), MEDLINE (July, week 3, 2017) and Embase (July week 31, 2017). Trial registries and journals were also searched as part of the update. Randomised controlled trials (RCTs) or controlled trials of NSAIDs in the treatment of CIN. Three review authors independently abstracted data and assessed risks of bias in accordance with Cochrane methodology. Outcome data were pooled using fixed-effect meta-analyses. In three RCTs, 171 women over the age of 18 years were randomised to receive celecoxib 400 mg daily for 14 to 18 weeks versus placebo (one study, 130 participants), celecoxib 200 mg twice daily by mouth for six months versus placebo (one study, 25 participants), or rofecoxib 25 mg once daily by mouth for three months versus placebo (one study, 16 participants). The study with rofecoxib was discontinued when the medicine was withdrawn from the market in 2004. The trials ran from June 2005 to April 2012, June 2002 to October 2003, and May to October 2004, respectively. We have chosen to include the data from the rofecoxib study as outcomes may be similar when other such NSAIDs are utilised.Partial or complete regression of CIN 2 or CIN 3 occurred in 31 out of 70 (44%) in the treatment arms and 19 of 62 (31%) in the placebo arms (risk ratio (RR) 1.45, 95% confidence interval (CI) 0.93 to 2.27; P value 0.10), three studies, 132 participants; moderate-certainty evidence). Complete regression of CIN 2 or CIN 3 occurred in 15 of 62 (24%) of those receiving celecoxib versus 10 of 54 (19%) of those receiving placebo (RR 1.31, 95% CI 0.65 to 2.67; P value 0.45, two studies, 116 participants; moderate-certainty evidence). Partial regression of CIN 2 or CIN 3 occurred in 14 of 62 (23%) of those receiving celecoxib versus 8 of 54 (15%) of those receiving placebo (RR 1.56, 95% CI 0.72 to 3.4; P value 0.26), two studies, 116 participants; moderate-certainty evidence).Progression to a higher grade of CIN, but not to invasive cancer, occurred in one of 12 (8%) of those receiving celecoxib and two of 13 (15%) receiving placebo (RR 0.54, 95% CI 0.05 to 5.24; P value 0.60, one study, 25 participants; very low-certainty evidence). Two studies reported no cases of progression to invasive cancer within the timeframe of the study. No toxicity was reported in the two original articles. The trial added in this update had one Grade 3 gastrointestinal adverse effect in the treatment arm, but otherwise had similar Grade 1 to 2 side effects between treatment and placebo groups. Although the studies were well-conducted and randomised, some risk of bias was detected in all studies. Furthermore, the duration of the studies was short, which may mask identifying progression to cancer.The addition of the trial in this update quadrupled the number of patients in the original review and was a well-designed multicentre trial thus, increasing the overall certainty of evidence from very low to moderate for this review. There are currently no convincing data to support a benefit for NSAIDs in the treatment of CIN. With the addition of this new, larger randomised trial we would rate this as overall moderate-certainty evidence by the GRADE criteria.