The aim of this study is to examine preservice science teachers' skills of formulating hypotheses and identifying variables. The research has a phenomenological research design. The data was gathered qualitatively. In this study, preservice science teachers were first given two scenarios (Scenario-1 & Scenario-2) containing two different research problems, which examined in detail preservice science teachers' skills of formulating a hypothesis and identifying variables. Then, pre-service science teachers were divided into three groups (those who formulate a hypothesis and identify variables correctly, partially correctly, and incorrectly). Three pre-service science teachers were selected from each group. They were asked to teach formulating a hypothesis and identifying variables based on two scenarios (Scenario-3 & Scenario-4) and observed for confirmation. The gathered data were analyzed using both descriptive (Scenario-1 & Scenario-2) and content analyses (Scenario-3 & Scenario-4). Two hundred and five (205) senior preservice science teachers, studying at the Department of Science Teacher Education at a state university in Turkey, participated in the study. At the end of the study, the results showed that preservice science teachers' skill at formulating a hypothesis and identifying dependent, independent and control variables accurately was low; their skill at identifying and controlling variables accurately was especially lower. The data from observations also indicated that pre-service science teachers had difficulty even in defining a hypothesis, formulating a hypothesis based on a problem, exemplifying ideal hypotheses, and defining, identifying and controlling variables. One of the most important reasons why preservice science teachers were not able to identify variables accurately was that they mistook one for variable another. Preservice science teachers accepted their mistakes and made various excuses for their poor performance.