This paper presents equipment and procedures for on-card (in-situ) performance testing of biometric on-card comparison implementations using pre-existing databases of biometric samples. A DTW-based on-line signature on-card comparison implementation serves as an example test object. The test results presented are false match rates and false non-match rates over a range of decision thresholds on a per-test-subject basis. The results reveal considerable differences in the comparison-score frequency distribution among test subjects, which necessitates the setting of user-dependent decision thresholds or comparison-score normalization.