A wood- or barrel-aged sour beer is any lager, ale or hybrid beer, either a traditional style or a unique experimental beer that has been aged for a period of time in a wooden barrel or in contact with wood and has developed a bacterial induced natural acidity. This beer is aged in wood with the intention of introducing the micro flora present in the wood. Sometimes wood aging is intended to impart the particularly unique character of the wood, but wood-aged is not necessarily synonymous with imparting wood-flavors. Wood character can be characterized as a complex blend of vanillin and unique wood character. Wood-derived character can also be characterized by flavors of the product that was in the barrel during prior use. These wood-derived flavors, if present in this style, can be very low in character and barely perceived or evident or assertive as wood-derived flavors. Any degree of woodderived flavors should be in balance with other beer character. Fruit and herb/spiced versions may take on the hue, flavors and aromas of added ingredients. Usually bacteria and “wild” yeasts fermentation contributes complex esters and results in a dry to very dry beer. Ultimately a balance of flavor, aroma and mouthfeel are sought with the marriage of acidity, complex esters, and new beer with wood and/or barrel flavors. Beers in this style may or may not have Brettanomyces character. Brewers when entering this category should specify type of barrel used and any other special treatment or ingredients used. Competition managers may create style subcategories to differentiate between high alcohol and low alcohol beers and very dark and lighter colored beer as well as for fruit beers and non-fruit beers. Competitions may develop guidelines requesting brewers to specify what kind of wood (new or used oak, other wood varieties). The brewer may be asked to explain the special nature (wood used, base beer style(s) and achieved character) of the beer.