The primary purpose of this study was to collect evidence on the construct validity of grit using convergent, discriminant, and predictive validity principles. To accomplish this purpose and extend previous research on grit, college students from two schools completed an instrument comprised of a cognitive ability test, and a questionnaire. The questionnaire was comprised of existing and multiple measures of grit, interest, self-efficacy, locus of control, and conscientiousness along with a number of college success measures. Structural equation modeling was used as the primary statistical analysis technique. Factor analysis, correlation analysis, and path analysis were also used. First, the results from a series of exploratory factor analyses based on four sources of evidence revealed four different factor structures of grit: (a) two-factor structure comprised of perseverance of effort and consistency of interest, (b) three-factor structure comprised of goal attainment, focus, and perseverance, (c) four-factor structure comprised of perseverance of effort, consistency of interest, harmonious passion and obsessive passion, and (d) two-factor structure comprised of grit and passion. Second, the results based on four different path analysis models found conscientiousness to be the sole predictor of both GPA and long-term college goals. Conscientiousness was an even better predictor of college success than cognitive ability -- not grit. Third, a series of correlation analyses based on different measures of grit and conscientiousness found a statistically significant strong positive relationship between grit and conscientiousness. Fourth, the resulting confirmatory factor analysis' Pearson correlation coefficients revealed a statistically significant "strong" to "very strong" positive relationship among all five latent constructs: interest, self-efficacy, locus of control, conscientiousness, and grit. Finally, results from the structural equation model found interest to be a predictor of subjective college success and conscientiousness to be the dominant predictor of both subjective college success and objective college success. Overall, the results from this study indicate that grit was not only hardly distinguishable from conscientiousness and other motivational constructs, it disappeared altogether. The dominant predictor of college success was conscientiousness. The popularity around grit may just be in its name. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]