This study had the purpose of identifying the impact of the dissection experiment utilizing pig heart, whose structure is similar to that of human heart. on science-gifted middle-schoolers` understandings of heart structure. It targeted middle school students who were taking the course of ``the special class for the gifted in the local community`` located in Ulsan Metropolitan City. 36 students in the 8th grade science class for the gifted were selected as the subjects of the study. The study was proceeded in the following sequence: first, a set of pre-tests were conducted including the activity of drawing heart structure, the open-ended questionnaire survey on heart structure and function, and the survey on the attitude toward dissection experiment; then, after explaining the matters to be attended and the main contents, the dissection experiment was carried out utilizing a pig heart. After the experiment, a set of post-tests were administered like the pre-tests utilizing the three same measures - the activity of drawing heart structure, open-ended questionnaire survey, and the survey on the attitude toward dissection experiment. The findings of this study were as follows: First, this study showed that most students could draw exactly the external features and the internal structure of the heart after the activity of the dissection experiment. Second, directly dissecting the heart and specifically observing the heart structure, the gifted students could explain the characteristics of the blood vessel connected to the heart, and the valve structure related to the valve function. Moreover, even though it was difficult to understand the structure of the main artery, aorta and the main vein, vena cava and the principle of the heart pulsation, this research showed that the gifted students could comprehend the structure of blood vessel and the heart pulsation associated with the circulation of the blood. Finally, this study showed us that the gifted students had the positive attitude toward the dissection experiment which provided them with the real learning experience.