A commentary on the 'state of the art' of the pretreatment of wastewaters with emphasis on the removal of grit and screening practices and the importance of other preliminary treatment processes as essential first stages in most wastewater treatment systems. Note is made of the lack of attention paid to preliminary treatment processes historically and on the paucity of knowledge of the mechanisms involved even today. However, there are developments and not only are conventional preliminary treatment processes reviewed, new processes are discussed and an attempt is made to forecast future trends.