Logical reasoning skills of students enrolled in a general chemistry course at the University of Puerto Rico in Rio Piedras were measured using the Group Assessment of Logical Thinking (GALT) test. The results were used to determine the students' cognitive level (concrete, transitional, formal) as well as their level of performance by logical reasoning mode: mass/volume conservation, proportional reasoning, correlational reasoning, experimental variable control, probabilistic reasoning, and combinatorial reasoning. This information was used to identify particular deficiencies and gender effects, and to determine which logical reasoning modes were the best predictors of student performance in the general chemistry course. Statistical tests were also performed to analyze the relation between (i) operational level and final grade in both semesters of the course; (ii) GALT test results and performance in the ACS General Chemistry Examination; and (iii) operational level and student approach (algorithmic or conceptual) toward a test question that may be answered correctly using either strategy. (Contains 6 tables and 2 figures.)