The popularity of the filtered density function (FDF) has been steadily growing since its original conception in the 1990s. Within the past 3-5 years, there has been a much sharper increase in the number of investigators who have contributed to its further improvements and applications. As a result, the methodology has been used extensively for large eddy simulation (LES) of a variety of reactive flows. Thus we feel it is timely to devote a mini-symposium to this methodology.