Practice records from November 1994 to April 2000 were searched for cats with a diagnosis of osteoarthritis (OA). Signalment, historical features and findings, treatment and response to treatment were recorded with the aim of planning prospective studies. Thirty-one cases were found. The average age at presentation was 13·8 years (range, nine to 17 years); 67 per cent were female and 33 per cent male. Clinical signs noted included chronic changes of stiff/abnormal gait (12), difficulty/reluctance in jumping (20) and reluctance to move (five). Eleven cases had acute or chronic lameness. Seven of the records indicated that the cat had been overweight. Physical findings included thickened joints (23), pain on joint manipulation (seven) and crepitus (four).Twenty cases had been radiographed. Findings included osteophytes (14), sclerosis (10), periosteal new bone (four) and remodelling (three). Routine blood tests were performed in 15 cats and showed single abnormalities in five cases. Concurrent diseases diagnosed included hyperthyroidism, dental diseases and chronic renal failure. The final diagnosis had been based on the history, examination, diagnostic tests and response to treatment. The joints thought to have been affected by OA were as follows: bilateral elbows (12), bilateral stifles (four), bilateral elbows and stifles (four), unilateral elbow (three), bilateral hips (two), other combinations of joints (six). Seventeen cats had both meloxicam treatment and a follow-up examination (they may have had concurrent treatments). The clinical notes recorded whether the owners considered there to have been an improvement: three showed marked improvement, 11 showed moderate improvement, one showed no improvement, one had an inconclusive response, and side effects stopped treatment in one. One cat showed a marked improvement after treatment with courses of pentosan polysulphate.