Fire service field staff instructors seek and share information and use information sources during their instructional work of teaching, training and curriculum development. This study is the first attempt to study their information-seeking and sharing behaviors, which have not previously been investigated empirically. Twenty-five fire service instructors who are field staff instructors of the Fire Academy were recruited to participate in the study. Semi-structured interviews as primary data along with secondary data were employed and examined to answer the research questions. Today's firefighters' responsibilities cover a wide range of emergencies in areas such as firefighting, emergency medical care, hazardous materials incidents, rescue operations, terrorism and other emergency responses. The increasing complexity of the fire service requires firefighters to continually hone their skills and improve their knowledge of various hazards through training. This study's findings reveal that the field staff instructor participants rely extensively on multiple types of information sources, while seeking and sharing information during the instructional process. These sources include formal/institutional, informal/personal and group network-mediated sources of information. This study identifies three collaborative information-seeking forms of joint, tag team, and intra-group and categorizes sequences of information activities the instructor participants undertake. It also characterizes their unique attributes as information seekers. Fire service knowledge structures of KSA--(Knowledge [cognitive], Skills [psychomotor] and Affective [attitude])--influence the changing needs of instructor participants, define the boundaries of information sources in these three required domain areas that firefighters learn and train, and dictate multiple types of information sources that are used and needed by the instructor participants. The dynamic nature and uncertainty of the fire service business as well as the task complexity are basic catalysts for the instructor participants' information-seeking and sharing behaviors, which motivate them to keep seeking the best piece of information to ensure the safety of firefighters. The Recognition-Primed Decision model leads instructor participants toward a heavy reliance on experiential knowledge. Furthermore, the selection of information sources is determined by the quality of the source, and multiple types of sources of information are constantly integrated to meet the field staff instructors' constantly changing needs. Armed with new evidence, this study revises and expands Leckie's model of information-seeking of professionals. This study recognizes the critical roles of field staff instructors in fire service training as they create, retain and share knowledge, skills and experience. The study also conceptualizes their multi-dimensional information environment with a cyclical and interactive information-seeking process that would best support their work activities. It makes suggestions for future research and lays out recommendations to improve library and information services, so fire librarians and information professionals can better provide more timely services to support fire service field staff instructors' information-seeking and sharing in a complex information use environment for their daily work, practices, and routines. [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.]