Background: Obesity is related to underestimation of one's own weight. Aim: To determine the agreement between nutritional status and self perception of weight status in apparently healthy adults from Talca. Subjects and methods: Data were obtained from a survey applied at 1007 randomly selected subjects, aged 18-74 years old (66% women). The survey identified age, gender, educational level and socioeconomic status. Self-perception of weight was estimated with pictures representing the four nutritional status categories: underweight, normal, overweight and obese. Body Mass Index (BMI, kg/m(2)) was calculated to determine nutritional status. Statistical analysis included kappa index. Bowmans symmetry test and a logistic regression model to calculate the odds ratio in different variables related to underestimation of weight. Results: Seventy three percent of subjects were overweight or obese and 44% underestimated their nutritional status. Sixty percent of subjects with a BMI between 25 and 26 kg/m(2), perceived themselves as normal. A higher underestimation was observed in obese subjects (odds ratio (OR) 17.2 95016 confidence intervals (CI) 10.9-27.1), in overweight individuals (OR 3.5 95% CI 2.3-5-3), in men (OR 1.5 95% CI 1.1-2.1) and in people aged from 45 to 59 years (OR 1.7 95% CI 1.0-2.7). Conclusion: Almost half of studied population had an erroneous self-perception of weight, mainly due to underestimation. Obese subjects, males and people older than 45 years were those with the higher degree of underestimation (Rev Med Chile 2009; 137: 76-82).