The first international specialty conference on deep mixing was co-organised by the Japanese Geotechnical Society (JGS) and the International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE) TC-17 in 1996 in Tokyo. The 1996 Tokyo conference was followed by a series of specialty conferences/symposia in 1999 Stockholm, 2002 Tokyo, 2005 Stockholm, and 2009 Okinawa. 2015 was the first event in the series to be held in North America outside Japan and Sweden. A subsequent conference was scheduled to be held in Poland in 2020, but was postponed due to Covid-19 and was eventually held as an online conference in 2021 as an alternative. The conference was successfully organised as an online conference. The conference will return to Japan in 2024. The Deep Mixing conference provides a platform for the worldwide exchange of the latest information on equipment, material properties, case studies, design procedures, quality control (QC) and quality assurance (QA), and environmental aspects of deep mixing.