Analysis of the temporal trend in obesity shows the increasing risk posed by this condition worldwide. This article aims to verify and compare the prevalence rates for overweight and obesity in male adolescents in all States of Brazil, from 1980 to 2005. We used the Brazilian Army's database, with 8,989,508 males 17-19 years of age. We defined overweight as body mass index (BMI) from 25 kg/m2 to 29.9 kg/m2 and obesity as BMI>or=30 kg/m2. The analysis showed an increasing trend in the prevalence of overweight and obesity in all States of Brazil for the period studied. There was a three-fold increase in adolescents with overweight and a six-fold increase in obesity. The absolute numbers for overweight were higher than for obesity, but the rate of increase over the period was greater for obesity. Analyzing the trend in prevalence rates by five-year period, we observed that from 1980 to 2005, as the prevalence of overweight decreased, that of obesity increased in all States of Brazil.