Double tracking of barium in the sigmoid colon has been associated with granulomatous colitis by some; others consider it a sign of peridiverticulitis. Patients who showed no evidence of inflammatory disease elsewhere in the large intestine were analysed. The pathological diagnosis was diverticulitis in 29 of 35 cases, and granulomatous diverticulitis in only 1. In 5 the underlying process was perforated carcinoma of the sigmoid colon. In those with paracolonic sinus tracts due to peridiverticulitis, pathological study demonstrated tracts extrinsic to the muscularis and usually traceable to a perforated diverticulum. Long-term follow-up disclosed no evidence of subsequent inflammatory bowel disease.