One hundred and four consecutive patients with pyrophosphate arthropathy were followed prospectively and re-studied at a mean of 4.6 years. Sixty-four patients (43F, 21M; mean age at review 71.2 years) completed the study (24 died of unrelated disease, 16 were unavailable for review). The knee had been the major presenting joint in 91%. Symptoms were improved in 41%, unchanged in 33% and had worsened in only 27%: 27% developed symptoms in new joints. Radiographic changes of arthropathy were unaltered in 50%: although 'worsening' of previously involved joints was seen in 16%, the most common change was increase in osteophyte with bone remodelling (31%). Despite dynamic changes in chondrocalcinosis in most patients (77%) there was no correlation between extent of calcification and progression of arthropathy. It is concluded that the outcome of pyrophosphate arthropathy is not necessarily progressive, patients presenting with acute attacks alone do particularly well.