Objective: To investigate the effect of duration of clinical training placements in the Northern Territory on rate of return of medical students for an internship in the NT.

Design, setting and participants: Retrospective analysis of medical school and hospital data on all medical students who completed a placement with the Northern Territory Clinical School (NTCS) between 1998 and 2007.

Main outcome measures: Logistic regression analysis of weeks spent training in the NT against the binary category of return or non-return for an internship in the NT; number of weeks of placement in the NT required for one returning intern for training models with different placement duration and timing.

Results: 683 students completed an NTCS placement: short-term Year 4 placements only, 538 (duration, 1–19 weeks, 534; and ≥ 20 weeks, 4); Year 3 40-week placements only, 16; and both Year 3 and Year 4 placements,129 (Year 4 duration, 1–19 weeks, 82; and ≥ 20 weeks, 47). For each student who returned for an NT internship, 122 weeks of placement were required. Placement length was a significant predictor of an NT internship (P < 0.05; odds ratio, 1.08; 95% CI, 1.07–1.09). The most efficient training models (fewest weeks per returning intern) were longer placements (≥ 20 weeks) in Year 4, both for students who also undertook a 40-week Year 3 placement and those who did not (90 and 47 weeks of training per intern, respectively). Students who spent only brief periods in the NT in Year 4 were less likely to return for an internship (P < 0.05). Conclusions: The rate of return increased with the total length of time spent training in the NT. Short-term Year 4 placements offered the least return for the total number of weeks of placement provided.