The purpose of the drawing method is to reveal the hidden beliefs, attitudes, knowledge and understanding of students without being dependent on words. It is more useful than other techniques in that it is easy to apply and a lot of data can be obtained with a drawing. Some misconceptions can be revealed by asking students to describe or illustrate some objects or phenomena. Biology is mostly concerned with the diagnosis of structures, their interrelationships and their functions. For this reason, it is very important to draw the biological structures correctly. Human circulatory system' comprehension is a major point in biology education. Because understanding this system is a basis for learning the transport and exchange of substances in the human body, the lymphatic system, gas exchange, and other important biological concepts. The aim of this study is to examine the cognitive structures of biology teacher candidates about the "circulatory system" with the drawing technique. In this study, a case study was conducted to reveal the biology teacher candidates' drawings in detail. In order to explore biology teacher candidates' drawing of the circulatory system in detail, their drawings were collected as data through 32 high school students (teacher candidates) in biology education faculty from Turkey. After the drawings were completed, each drawing was effectively scored for the presence or absence of at least one organ/structure in circulatory system. In addition, the drawings were further reclassified, taking into account the pattern of the path of pulmonary and systemic circulations. According to the findings obtained from the drawings of the biology teacher candidates about the circulatory system, it was revealed that the teacher candidates had many misconceptions, mistakes and incomplete information.