Struvite in wastewater treatment plants was identified as early as 1939. Problems with struvite formation date back to the 1960s when it was noticed at the Hyperion treatment plant, Los Angeles. Operators at the plant noticed crystalline deposits on the underside of post digestion screens. The digested sludge stream was diluted and it was thought the problem was solved, until five years later when the normal gravity flow of digested sludge had decreased to such a stage that pumping was required. This paper reports the findings of a series of experiments undertaken to identify the potential of recovering struvite from sludge liquors. Seven sludge treatment works (STW) have been investigated including one detail. A number of the works has the potential to form over 100 mg l(-1) of struvite.