This study is an investigation of relationships among impulsiveness, locus of control, sex, observed practice behaviors, practice effectiveness, and self-reported practice habits in a sample of 40 college brass players. Practice effectiveness was defined by the amount of change in pretest and posttest performance achievement scores over one 23minute practice session. Each subject's practice session was analyzed for frequency of practice behaviors. Measures included the Eysenck Impulsiveness Questionnaire for Adults (1985), the Nowicki-Duke Locus of Control Scale for Adults (1974), and a researcher-designed practice questionnaire. Results indicated (a) a significant interaction effect (p < . 01) between performance achievement and impulsiveness, with subjects in the low-impulsive group outperforming those in the high-impulsive group; (b) a significant relationship ( p < . 01) between subjects' locus of control and impulsiveness scores; (c) no significant differences ( p > .05) in impulsiveness, locus of control, or performance achievement by sex; (d) significant relationships ( p < .05) between performance achievement and the observed practice behaviors "repeat section, " "whole-part-whole, " "marks part, " and "varying pitch"; and (e) no significant relations ( p > .05) between amount of time spent playing during the practice session in the study and performance achievement.The author would like to thank Dr. Charles P. Schmidt of Indiana University in Bloomington for his advice and guidance throughout the develpment of this project. Peter Miksza is a doctoral candidate in music education at Indiana University.Education.The ability to practice effectively is essential for developing musicperformance skills. However, as many students, teachers, and researchers have come to understand, defining what constitutes effective practicing is difficult. As a result, researchers have taken a variety of methodological approaches to the study of music practicing. Practicing has been examined by means of self-report (e.g.,