Objective: Although septal myectomy (SM) is the preferred treatment for medication-refractory obstructive hypertrophic cardiomyopathy, the procedure remains subjective. We have developed a virtual myectomy (VM) technique using 3-dimensional reconstruction of gated cardiac computed tomography (CT) to assist intraoperative objective assessment of the adequacy of the resection. Methods: We retrospectively reviewed patients 15 patients who underwent a SM guided by preoperative VM at our program between March 2016 and July 2017. Gated cardiac CT was performed to allow delineation of the left ventricular (LV) myocardium at end-diastole to replicate the cardioplegic myocardial arrest (90%-95% RR interval). SM was performed to attain resection volume predicted by VM. Retrospective, blinded VM also was performed with fixed parameters to determine relationship between ideal (VM1) and conservative (VM2) VM and actual resection. Results: Mean patient age was 52.1 ± 10.6 years, 27% were male, and 80% had New York Heart Association class 3 or 4. Preoperative mean peak LV outflow tract gradient was 79 mm Hg (range 47-82). In-hospital mortality was 0%. Mean postoperative LV outflow tract gradient was 13 mm Hg (11-19). Gated cardiac CT was performed with mean phase 94% (86%-98%). Mean total LV myocardial volume was 226 cm3 (146-365) and volume of the asymmetric portion of the LV was 19 cm3 (5.2-48.8). Actual surgical resection volume was 6.2 ± 1.7 cm3. Retrospective VM1 and VM2 performed postoperatively blinded to surgical results were 12.8 cm3 (4.8-29.23) and 6.7 cm3 (3.5-13.2), showing a modest correlation (R1 = 0.44, R2 = 0.56) with actual myectomy. Conclusions: Three-dimensional CT and VM can be a viable addition to preoperative assessment of patients with obstructive hypertrophic cardiomyopathy.