The symposium will attempt to provide an understanding of the behavioral and psycho-physiological research literature on mental practice/imagery (MP) related to motor and sport performance.  Daniel Landers will briefly review the overall effects of MP on motor performance as well as selected moderator variables which have implications for (a) when MP should be given relative to physical practice (PP) and (b) the number of MP trials required for different types of motor tasks.  Shawn Arent will describe research findings dealing with procedural variables associated with MP (i.e., whether MP should come before or after PP and the length of MP sessions).  Rafer Lutz will review the research literature on "internal/external" and "outcome/form" focus during motor imagery and then describe research which shows that, if MP is given to elite athletes who already have preperformance routines, performance will be impaired.  Penny McCullagh will describe a confounding factor in MP studies--that of demonstrating the skill prior to participants engaging in MP.  She will review two recent studies that have shown that modeling effects are greater than MP effects.  Diana Romero will review changes in heart rate, respiration rate, and brain activity, and Justin Slade will review changes in muscular activity (EMG), associated with real and imagined movements.  These findings show that, compared with real movements, the patterning of physiological activity associated with MP is not exactly the same for heart rate, respiration, and cortical measures, but there is considerable functional equivalence.  However, there is no functional equivalence between real and imagined movements when muscular (EMG) measures are examined.  Daniel Landers will conclude the symposium with a synopsis of gaps in our present scientific knowledge of MP, as well as what the current research literature means for practitioners in the field.