The purpose of this communication is to present a method that assesses the sigmoid colon (SC) volume, pressure and compliance both quantitatively and qualitatively. The response of the SC pressure to SC distension was recorded in 12 healthy volunteers. The SC was distended by means of a condom, which was applied to an 8 F tube and inflated with carbon dioxide at a rate of 150 ml/min. The SC pressure was measured by a saline-perfused 8 F tube and the intra-abdominal pressure by a catheter placed in the urinary bladder. A curve called 'sigmoidometrogram' could be recorded and assessed qualitatively and quantitatively. The curve had a 'tone limb' representing the SC pressure upon distension and an 'evacuation limb' representing the SC pressure during balloon expulsion. The former showed insignificant pressure elevation (P > 0.05) with increasing volumes of CO2 inflation. It exhibited minor fluctuations which paralleled those of the intra-abdominal pressure. The 'evacuation limb' described a curve with an ascending limb continuous with the tone limb and a descending one, which descended vertically to the base line. Quantitatively, the infused CO2 volume and intrasigmoid and intra-abdominal pressures could be determined from the curve at each of the distension and expulsion sensation. Consequently, the SC compliance could be calculated. A normal sigmoidometrogram seems to reflect the normality of the sigmoid wall structure, afferent axons and central sensory pathways. Alteration of any of the components of this pathway is expected to change the measurements of SC volumes, pressure, compliance and sensation; it would also disturb the morphometry of the curve.