Studies in adult learning have increased and better developed in the past century. From them adult learning theory emerged, comprised of andragogy, self-directed learning, and transformational learning. The main purpose of this study is to measure the teaching style preferences of trainees at a mid-size police department. The second purpose is to identify the differences in trainees' teaching style preferences depending on six factors. This study is primarily quantitative and is based on a survey design. The sample included 209 police officers, who were, at the time of study, working at Louisville Metro Police Department, Louisville, Kentucky. The researcher used the Principles of Adult Learning Scale (PALS) survey instrument for measurement and gathered demographic data using six additional questions. To understand the differences among demographic groups, he used the Multivariate Analysis of Variance (MANOVA) test as well as six Analysis of Variance (ANOVA) tests. Finally, eight t-Test analyses were used to see the difference between the score of the participants and the mean norm score of PALS. The results indicated significant differences in years of service and level of education based on the teaching style preference scores. They revealed no significant difference among demographic groups based on the overall PALS score. However, the overall mean score showed a strong tendency toward a teacher-centered instruction. This study will help police instructors and administrators in police academies create and awareness about the teaching style preferences of the trainees in police in-service training and, in turn, aid instructors in creating more effective learning environments for police officers. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]