To analyze the clinical features and colpohistology of women with vaginal intraepithelial neoplasia (VAIN). Patients with VAIN treated at Rajavithi Hospital between April 1986 and October 2007. Of 68 patients, 52.9% had VAIN2/3. The mean age of patients was 50.85 +/- 13.17 years (range: 22-80). The most common presentation was abnormal cytology. History of prior pelvic radiation, associated neoplasia of the lower genital tract and history of prior hysterectomy were documented in 7.4, 67.6 and 54.4% of patients, respectively. Median intervals from previous lower genital tract neoplasia to current diagnosis of VAIN, and between hysterectomy to diagnosis of VAIN were 23.9 and 29.7 months, respectively. The upper third of the vagina was the most common site of VAIN (86.8%). The most common colposcopic finding was the presence of acetowhite epithelium. Punctation was significantly associated with VAIN2/3 (P < 0.05). Mosaic was rare and found in VAIN3. VAIN can occur at any age and is commonly associated with neoplasia of the lower genital tract. Most patients have disease located in the upper third of the vagina. The most common colposcopic finding is acetowhite epithelium while punctation and mosaic pattern are more prevalent in VAIN2/3.