Context Clinical skills assessment using standardized patients (SPs) is an accepted method of professional testing, but some factors can threaten the validity of the scores obtained. Objective The main objective of this work was to test whether the gender of the patients, the sequence of cases and the day of the examination have any impact on the scores of the examinees. Materials Data from examinations conducted at three Medical Schools are used. Each student encountered 10 different SPs (5 men and 5 women). Methods Analysis of variance was used to test the existence of association between the variables. Results The results showed no signi®cant differences or association between the scores and the three variables analysed. Conclusions The results are coherent with the studies that show that performance based examination using SPs can be used without introducing biases into students score