This paper focuses on the use of virtual fixtures to improve the learning of basic skills for laparoscopic surgery. Five virtual fixtures are defined, integrated into a virtual surgical simulator and used to define an experimental setup based on a trajectory following task. 46 subjects among surgeons and residents underwent a training session based on the proposed setup. Their performance has been logged and used to identify the effect of virtual fixtures on the learning curve from the point of view of accuracy and completion time. Virtual fixtures prove to be effective in improving the learning and affect differently accuracy and completion time. This suggests the possibility to tailor virtual fixtures on the specific task requirements. ; Peer Reviewed ; Postprint (published version)