Lambic is a very distinctive type of beer brewed only in the Pajottenland region of Belgium (southwest of Brussels) and in Brussels itself at the Cantillon Brewery and museum. Lambic is now mainly consumed after refermentation, resulting in derived beers such as Geuze or Kriek.

Unlike conventional ales and lagers, which are fermented by carefully cultivated strains of brewer's yeasts, lambic beer is produced by spontaneous fermentation: it is exposed to the wild yeasts and bacteria that are said to be native to the Senne valley, in which Brussels lies. It is this unusual process which gives the beer its distinctive flavour: dry, vinous, and cidery, usually with a sour aftertaste.

The origins of lambic beer lie in the working classes of the region some 500 years ago who appreciated a weak, quenching drink that could be produced cheaply and easily on the farm.

Since then, the style has diversified to a wide range of styles, strengths, and social classes.

Today the beer is generally brewed from a grist containing approximately 70% barley malt and 30% unmalted wheat. When the wort has cooled, it is left exposed to the open air so that fermentation may occur spontaneously. While this exposure is a critical feature of the style, many of the key yeasts and bacteria are now understood to reside within the brewery and its (usually timber) fermenting vessels in numbers far greater than any delivered by the breeze. Up to 86 microorganisms have been identified in lambic beer, the most significant being Brettanomyces bruxellensis and B. lambicus. The process is generally only possible between October and May as in the summer months there are too many unfavourable organisms in the air that could spoil the beer.

Lambic beer is widely consumed in Brussels and environs, and frequently featured as an ingredient in Belgian cuisine.

Quadrupel is a type of strong ale, brewed in the Belgian style. Brands of quadrupels include La Trappe Quadrupel brewed by De Koningshoeven Brewery in the Netherlands, and Saint Louis Brewery's seasonal Schlafly Quadrupel Ale.

In other countries, particularly the United States, 'quadrupel' or 'quad' may refer to an especially strong style of dark ale, with a characteristic spicy, ripe fruit flavor.

A quadrupel is intended to be stronger than a Tripel, so the ABV strength will be 10 % or more. Beyond that, there is little agreement on the status of quadrupel as a style.

Saison is the name originally given to low-alcohol pale ales brewed seasonally in farmhouses in Wallonia, the French-speaking region of Belgium, for farm workers during harvest season. Modern-day saisons are also brewed in other countries, particularly the USA, and are generally bottle conditioned, with an average range of 5 to 8% abv, though saisons at the more traditional 3.5% strength can still be found.

Although saison has been described as an endangered style, there has been a rise in interest in this style in recent years, with Saison Dupont being named “the Best Beer in the World” by the magazine Men’s Journal in July 2005.

Historically, saisons did not share identifiable characteristics to pin them down as a style, but rather were a group of refreshing summer ales. Each farm brewer would make his own distinctive version. Modern saisons brewed in the USA tend to copy the yeast used by Brasserie Dupont, which ferments better at blood warm temperatures (29 °C