Objective: The purpose of this study was to illuminate STEM students’ perceptions of internship experiences and to examine the impact of these experiences on career and college major choices and retention in the science career pipeline. Background: Many high schools operate internship programs with the purpose of providing authentic work experiences. Through these experiences, students are forced to confront the unrealistic nature of their personal perceptions of practice, and are then exposed to the nuances of practice and authentic skills of practice. Methods: Students were asked to complete an internship questionnaire as part of the senior exit process along with a traditional senior exit survey. The internship questionnaire was an outgrowth of items originally used and piloted on an original exit survey from prior years. Follow up interviews in individual and group settings were used to clarify survey responses. Data were coded through a qualitative analysis and themes were illuminated in the responses. Results: Perception and impact varied on the basis of career choice fluctuation in high school (i.e., static science; dynamic science; non-science-to-science; static non-science and science-to-non-science changers). Influence varied in strength among the various career fluctuation groups in relation to college major, career choice and retention in the science pipeline. Conclusion: No doubt, the internship process is impacting on high school students. The nature of this impact is dependent upon the career orientations of individuals. In the present study, dynamic science students (i.e., individuals who changed from one science career to another during high school) showed the strongest response in relation to the ability of internships to produce retention in the science pipeline. The non-science-to-science career changers showed the strongest responses with respect to internship impact on college major and career choice. The science-to-non-science changers showed consistent and marginal impact responses and very few described internships as impacting. Static science students found internships to be especially impacting on career choice and on retention. Lastly, static non-science students acknowledged general impact of internships. Application: This descriptive study can serve as a basis for further research focusing on the causal relationships and identification of key factors that influence the impact of internship situations.