Résumé : Objectives: Identify and prospectively investigate simulated ultrasound-guided targeted liver biopsy performance metrics as differentiators between levels of expertise in interventional radiology. Methods: Task analysis produced detailed procedural step documentation allowing identification of critical procedure steps and performance metrics for use in a virtual reality ultrasound-guided targeted liver biopsy procedure. Consultant (n 5 14, male 5 11, female 5 3) and trainee (n 5 26, male 5 19, female 5 7) scores on the performance metrics were compared. Ethical approval was granted by the Liverpool Research Ethics Committee (UK). Independent t-tests and analysis of variance (ANOVA) investigated differences between groups. Results: Independent t-tests revealed significant differences between trainees and consultants on 3 performance metrics: targeting, p 5 0.018, t 5 22.487 (22.040 to 20.207); probe usage time, p 5 0.040, t 5 2.132 (11.064 to 427.983); mean needle length in beam, p 5 0.029, t 5 22.272 (20.028 to 20.002). ANOVA reported significant differences across years of experience (0-1, 1-2, 3+ years) on seven performance metrics: no-go area touched, p 5 0.012; targeting, p 5 0.025; length of session, p 5 0.024; probe usage time, p 5 0.025; total needle distance moved, p 5 0.038; number of skin contacts, p , 0.001; total time in no-go area, p 5 0.008. More experienced participants consistently received better performance scores on all 19 performance metrics. Conclusion: It is possible to measure and monitor performance using simulation, with performance metrics providing feedback on skill level and differentiating levels of expertise. However, a transfer of training study is required.