In Taiwan, the Science Volunteer Locomotive (SVL) Program has been in operation for the past ten years. During these years of its implementation, the SVL Program has continued to participate in and co-ordinate various national scientific activities. This study examined the relationships between volunteers' prime motivations, self-directed learning and satisfaction among Taiwanese science volunteers. To explore volunteers' perspectives on their involvement in science service, in this research, we developed three questionnaires to investigate the relationships among volunteers' motivation, self-directed learning and satisfaction with their science service. The study sample included 289 volunteers, taken from a project for science volunteers run by the Ministry of Science and Technology in Taiwan. The results indicate that the prime motivations and self-directed learning of science volunteers are focused on doing something meaningful for others and for society in general. It was found that the science volunteers' motivation, self-directed learning and satisfaction all had significant positive correlations. The findings suggest that science training programs may provide some motivational support to enhance satisfaction, so that science volunteers will be more inclined to participate in collaborative scientific projects.