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 23-minute 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 less than 0.01) between performance achievement and impulsiveness, with subjects in the low-impulsive group outperforming those in the high-impulsive group; (b) a significant relationship (p less than 0.01) between subjects' locus of control and impulsiveness scores; (c) no significant differences (p greater than 0.05) in impulsiveness, locus of control, or performance achievement by sex; (d) significant relationships (p less than 0.05) between performance achievement and the observed practice behaviors "repeat section," "whole-part-whole," "marks part," and "varying pitch"; and (e) no significant relations (p greater than 0.05) between amount of time spent playing during the practice session in the study and performance achievement. (Contains 1 figure and 4 tables.)