High resolution anorectal manometry has been developed over the past years, as well as 3D high definition manometry (HDARM). However, the clinical impact of the results obtained with these new technologies remains to be determined. We thus analyzed various HDARM parameters of anal sphincter function and tested their capacity to discriminate between patients with constipation and those with fecal incontinence. One hundred and fourteen consecutive patients underwent the same HDARM protocol (Medtronic), including 2 short duration voluntary anal contractions (5seconds) and 1 sustained (as long as possible) contraction. Various parameters evaluating the anal sphincter function were measured, based on automatic software analysis and Smartmouse™ item of the software; resting anal pressures, anal pressures and incremental pressures during voluntary squeeze and cough anal reflex. The ability of these parameters to discriminate between patients with fecal incontinence and chronic constipation was assessed using areas under the curves of ROC curves. All parameters were highly correlated. The most discriminant variable was found to be the mean anal pressure during sustained squeeze. The 3D lambda aspect of the anal sphincter during voluntary contraction was as frequently absent in both groups of patients (13% in patients with chronic constipation, versus 23% in those with fecal incontinence, P=0.18). There was a significant correlation between the fecal incontinence Wexner score and the voluntary anal contraction variables. Several parameters to assess the quality of voluntary anal contraction have been proposed. We observed with HDARM that the most discriminant parameter was the mean anal pressure during sustained squeeze. This may help to standardize and simplify HDARM protocols.