BACKGROUND AND STUDY AIMS: Squamous cell carcinoma of the esophagus (SCCE) becomes symptomatic at a late stage when the disease is already advanced, and this contributes to its poor prognosis. Esophagoscopy of asymptomatic individuals exposed to known risk factors associated with the development of this cancer may facilitate the diagnosis of early cancerous or precancerous lesions; however, conventional esophagoscopy is not accurate enough. The aim of this study was to measure the value of Lugol chromoendoscopy of the esophagus (LCE) as an endoscopic technique to detect dysplasia in patients at risk. PATIENTS AND METHODS: We studied 190 male patients older than 35 attending an outpatient unit for alcoholics who consumed more than 80g of alcohol, more than 10 cigarettes and more than 500 ml 'maté' (a hot infusion of herbs) per day over 10 years. All underwent conventional upper gastrointestinal endoscopy followed by LCE, a spraying of Lugol 3% on the entire esophagus. All patients denied dysphagia. Biopsies were obtained from any unstained areas larger than 5mm and also from stained areas in all individuals. Biopsies were analyzed independently by two pathologists unaware of the biopsy sites. All conventional esophagoscopies showed normal mucosa, except for two suspicious small elevated lesions, confirmed histologically to be SCCE. These two cases were excluded from the statistical analysis. RESULTS: The LCE found unstained areas in 23 patients and a uniformly stained esophageal mucosa in the remaining 165. Biopsies taken from these 23 unstained areas showed dysplasia in six (two high grade and four low grade), and the ones from the 165 stained areas taken at the middle esophagus showed low-grade dysplasia in seven. There was a high prevalence (6.9%) of dysplastic lesions in these individuals and occult dysplasia was significantly more frequent in unstained than stained areas (p = 0.0017). LCE showed a sensitivity of 46%, a specificity of 90%, a positive predictive value of 26% and a negative predicitve value of 96% when unstained areas were compared to stained ones. Agreement between two independent pathologists was high, with a kappa coefficient of 0.64. CONCLUSION: We concluded that individuals who abuse alcohol, smoke and consume 'maté' have a high prevalence of dysplastic lesions that can be better detected by LCE. Esophagi with unstained areas had an eight-fold higher chance of revealing dysplasia than the uniformly stained ones. LCE is an easy and inexpensive method. It improves the detection of dysplasia and should be added to conventional upper GI endoscopy in patients at risk for SCCE.