Science advances through the introduction of new paradigms and shifts in paradigms that dominate particular knowledge domains.  The science base of STD prevention is no different; epidemiology and public health science have evolved through a number of paradigm shifts.  This session will feature three talks which use scientific developments closely related to STD/HIV prevention to demonstrate currently emerging scientific paradigms and their implications for improved understanding of STD/HIV spread and prevention.  The first talk will describe the evolving science base for STD/HIV prevention programs, including their planning, development, implementation, and evaluation and with particular attention to improving allocative and program efficiency, effectiveness and sustainability.  The second talk will highlight the importance of mathematical modeling which has emerged as the key methodology used in policy science.  It will include examples of recent mathematical modeling analyses which have facilitated key policy decisions in the area of STD/HIV prevention.  The last talk will introduce complexity science as a scientific paradigm and discuss the implications of approaching transmission, prevention, health care and health services as complex systems for STD/HIV prevention.  The session will conclude with an interactive discussion of these emerging scientific paradigms and their impact on STD epidemiology and prevention.