The purpose of this study was to construct and evaluate an instrument for determining student preparedness in College Algebra. A 73-item instrument covering prerequisite arithmetic and high school Algebra knowledge for College Algebra was constructed. The instrument was pilot-tested on a freshman population of 595 students. Results of reliability testing using the split odd-even test showed that the instrument is reliable at a 0.05 significance level. Concurrent and predictive validity testing likewise showed that the instrument is valid (a = 0.05). Students who scored at least 56 out of 73 in the instrument were found to be much more likely to pass a College Algebra course than those who scored less than 56 (p is approximately equal to 0.00). Item analysis showed that 71% of the items have acceptable discriminatory indices. The remaining 29% were considered for revision or removal. It was recommended that the instrument be refined based on the outcomes of the evaluation and that it be subsequently administered to other freshman populations prior to taking their respective College Algebra courses. (Contains 1 figure.) [This paper was published in: Proceedings of the Mathematics Teachers Association of the Philippines Tertiary Level Annual Convention, West Visayas State University, Iloilo City, Philippines, August 30-31, 2008.]