1. Osteitis condensans ilii represents an alteration in the normal bony architecture of that portion of the ilium alongside the sacro-iliac joint. The authors' observations thus far suggest that this occurs as the result-of mechanical strain affecting an amphiarthrodial joint. Further investigation regarding the etiology and the pathology of this condition is under way.
2. A careful differential diagnosis must be made between osteitis condensans ilii and Marie-Strümpell arthritis, with which it has been confused in the past. Contrary to the authors' own original impressions, sacro-iliac tests are seldom positive in osteitis condensans ilii, while the blood sedimentation rate is usually within normal limits.
3. Again in contrast to the experience of earlier workers, the authors have demonstrated roentgenographically in six patients that this process is reversible.
4. Of 100 patients revielled, eight showed no response to treatment and twenty-three were somewhat improved; in sixty-seven patients conservative treatment afforded either complete relief or marked amelioration of symptoms. Surgical intervention was necessary in only two instances.