Systemic sclerosis (SS) alters smooth muscle function throughout the gastrointestinal tract, the oesophagus being the segment most often involved. Involvement of the colon, though less common, may lead to life-threatening complications. We studied 23 unselected patients with SS and 20 age-matched healthy controls using radionuclide colon transit studies. The geometric centre (GC) at 4 and 24 hours was used to summarise overall transit in the colon. In patients with SS, colon transit was delayed (GC4: 0.39 +/- 0.36 vs 0.85 +/- 0.45; P=0.001) (GC24: 1.68 +/- 0.9 vs 2.58 +/- 1.08; P=0.006). These findings suggest that delayed colon transit is common in patients with SS.