Despite the recognized health benefits of activity involvement for individuals of all ages, it is estimated that only 30% of the U. S. population age 18 years and older engage regularly in moderate leisure-time physical activity (National Center for Health Statistics, 2006). The inactivity issue is no more critical than among Mexican American women; when compared with Black or non-Hispanic White females, they were least likely to engage in moderate or vigorous physical activity and to be physically active during leisure (Ford, et al., 2001). Studies investigating factors that may explain the high prevalence of leisure-time physical inactivity in the general population have indicated perceived barriers play a powerful role in keeping people from being or becoming physically active. The purpose of the present study was to extend research dealing with leisure-time physical activity barriers to Mexican American females, a population group having the nation's greatest physical inactivity disparity. The sample was drawn from the parents and adult relatives of fourth and fifth grade students enrolled in four elementary schools of two school districts located in the Lower Rio Grande Valley region of Texas. Data were gathered through a self-report survey instrument, in both English and Spanish, consisting of physical activity level, health status, education, marital status, and physical activity barriers as well as the demographic variables of age, gender, and ethnicity. Four hundred thirty-six women (M age 35.3 years, SD=7.97; age range 23 to 62 years) served as study subjects. To determine what barriers influence physical inactivity, subjects were grouped into physically active and physically inactive categories and discriminant analysis was performed to test for variable associations between groups. Analysis identified lack of motivation followed by lack of time as the only statistically significant (p<.01) predictors of membership in the physically inactive or active groups. That is, physically inactive subjects reported inadequate motivation and time as the reasons for undermining their ability to make regular physical activity a priority. Findings suggest that interventions for promoting increased leisure-time physical activity among the population group studied focus on creating strategies designed to help overcome the perceived intrapersonal constraints of lack of motivation and time. Keyword(s): exercise/fitness/physical activity, multiculturalism/cultural diversity