The Mediterranean diet was first brought to the attention of the medical community in 1945 when a doctor who observed the lifestyle and health benefits of people in Salerno, Italy and wrote about it.  It was not until the 1990's that it became popular.  It is based on the eating habits of people such as those living in Crete, Greece and Southern Italy.  It was observed and research was done showing that there was a very small incidence of heart disease in these regions.  This was primarily attributed to the diet. The main features of the Mediterranean Diet is eating a lot of fresh foods like fruits and vegetables, having fish at least once a week, using olive oil as a primary source of fat, eating whole grains and certain dairy products regularly.  It has been favorably reviewed on sites like the Mayo Clinic and is praised for its heart healthy approach to eating.

Fresh Foods
Eat a variety of fresh fruits and vegetables during meals and even have them for snacks.  With this diet it is recommended that you eat 9 to 10 servings of fruits and vegetables a day. Whole grains are also a key part of the diet.  This allows for the complex carbohydrates to release their sugars in to the system slowly throughout the day, reducing the sugar and resulting, insulin spikes you will experience. 

Oils
The primary source of fats comes from olive oils which is excellent source of monounsaturated fats.  This is reported to lower cholesterol and even reduces peptic ulcers. Choose virgin or extra virgin olive oil because it has been processed the least.  The amount of fats is not as limited as many diets, but healthy fats are indicated. Never use trans-fats like hydrogenated oils.
The diet also recommends that you have fish regularly which is high in omega 3 oils

Meat
The primary source of protein is fish which should be eaten at least once a week.  Have chicken occasionally. Red meats, if eaten at all should be eaten only rarely.

Low fat dairy products can be eaten.  Instead of whole or 2 percent milk have skim.  Limit ice cream and cheese to rarely or very small portions. Have low fat cheese instead and include fat free yogurt.

One surprising element is that you can have a glass of wine with the meal. It is recommended that only low to moderate levels are consumed and that only with meals. If you should not drink alcoholic beverages grape juice has been recommended, although this may or may not provide the same benefit.

Summary: This is a clear example of a traditional diet that has a very beneficial impact on the rest of us.  The regional foods that are available to the Mediterranean community as well as the dietary choices provide an excellent model to maintain a healthy lifestyle that can be especially good for the heart. 

See also The South Beach Diet.  Dr. Agatston developed this popular diet based on principles of the Mediterranean diet.