A study explored possible reasons why technical and further education (TAFE) students enrolling in vocational education and training (VET) courses in New South Wales, Victoria, and Western Australia do not complete those courses. Findings were based on these two kinds of evidence: evidence obtained from a statistical investigation of the outcomes of course enrollments and that obtained from phone interviews with past students. The study focused on the relationship between course completion rates and course structure. Findings indicated that these two broad groups of factors influenced the rate of course completions: courses that are "bigger" have lower completion rates and courses that have more choice have lower completion rates. With respect to course size, the completion rate was lower in these instances: the more modules in a course, the more "core" modules in a course, the more "elective" modules in a course, or the longer the course in nominal hours. The completion rate was higher the greater the average module length. With respect to course choice, courses composed of core plus electives had lower completion rates that "core-only" courses; core-elective courses with more electives from which to choose had lower completion rates than those with fewer; and where students had to choose several electives (M) out of a larger number (N), the lower the value of M/N, the lower the completion rate. The interview schedule is appended. (Contains 67 endnotes, 38 tables, and 23 figures.) (YLB)