Catheter mapping was performed during sinus rhythm in 52 patients with 102 morphologically distinct ventricular tachycardias (VT). Twenty patients had a single VT morphologic pattern. The cycle length of VT was correlated with the duration of all electrograms and various electrogram subgroups, including abnormal, fractionated, late, and longest electrograms, as well as the electrogram recorded at the site of origin of VT and at sites other than the site of origin using linear regression analysis. No correlation was found between local electrogram duration of any of these groups and VT cycle length. There was no relation regardless of whether the patient had a single or multiple morphologic patterns. Thus, the local electrogram duration measured with catheter mapping during sinus rhythm does not correlate with VT cycle length. This finding provides additional support that catheter mapping during sinus rhythm does not give sufficient information to guide localized endocardial resection for VT surgery.