BACKGROUND: Dietary intake has changed considerably in South European countries, but whether those changes were similar between countries is currently unknown. AIM OF THE STUDY: To assess the trends in food availability in Portugal and four other Mediterranean countries from 1966 to 2003. METHODS: Food and Agricultural Organization food balance sheets from Portugal, France, Italy, Greece and Spain. Trends were assessed by linear regression. RESULTS: The per capita availability of calories has increased in Portugal, France, Greece, Italy and Spain in the past 40 years. Portugal presented the most rapid growth with an annual increase of 28.5 +/- 2.2 kcal (slope +/- standard error), or +1000 kcal overall. In animal products, Portugal had an annual increase of 20.7 +/- 0.9 kcal, much higher than the other four countries. Conversely, the availabilities of vegetable and fruit only showed a slight growth of 1.0 +/- 0.1 kcal/year and 2.5 +/- 0.4 kcal/year, respectively, thus increasing the ration of animal to vegetable products. Olive oil availability increased in all countries with the notable exception of Portugal, where a significant decrease was noted. Wine supply decreased in all five countries; in contrast, beer supply started to take up more alcohol share. Percentage of total calories from fat increased from nearly 25% to almost 35% in Portugal during the study period, mainly at the expenses of calories from carbohydrates, whereas the share of protein showed just a slight increase. Furthermore, fat and protein were increasingly provided by animal products. CONCLUSIONS: Portugal is gradually moving away from the traditional Mediterranean diet to a more Westernized diet as well as France, Greece, Italy and Spain. Noticeably, the trends of diet transition were observed relatively faster in Portugal than in the other four Mediterranean countries.