A 99mTc count profile of the sacro-iliac region was performed in 14 control subjects and in 50 patients with inflammatory pain of the sacro-iliac joints. In addition, 85mSr count profiles were recorded in 14 control subjects. The sacro-iliac/sacral uptake ratio was calculated. There was no significant difference between Sr and Tc count profiles. The uptake in patients with sacro-iliitis was not above the range for controls. The mean uptake ratio was significantly below that for controls, and was lower in cases with radiologically advanced changes than in those with few or no signs. This method was not useful for early diagnosis of sacro-iliitis.