Obesity, and especially morbid obesity, increases the risk of cardiovascular as well as non-cardiovascular diseases. Our objective was to ascertain the trends in morbid obesity in Spain from 1993 to 2006 using representative data from 106,048 participants in the National Health Surveys. An age-adjusted Poisson regression model stratified by sex was fitted using morbid obesity as the dependent variable. An increasing trend in prevalent morbid obesity from 1.8 to 6.1 per thousand participants was found (increase>200%). Morbid obesity prevalence was higher in women. After adjusting for age, a monotonically increasing prevalence of morbid obesity was apparent for both men and women: the relative increase was 4% per year in women and 12% per year in men. These trends highlight the importance of preventive actions.