The current study elucidated the reasons for athletic performance differences between individuals who (1) engage in similar workloads, and (2) develop in similar environments. 8 elite and 11 sub-elite swimmers, with confirming data provided by 17 of their parents and 6 of their coaches, participated in this investigation. Findings revealed that (1) a variety of different practice regimens can result in attaining expertise, and (2) highly analogous developmental experiences may not differentiate between elite and sub-elite performers. Results provide support for a 4-factor model of expert athletic development: high effort, supportive environment, facilitative coping strategies, and physical and psychological predispositions. Each is likely required to achieve elite athletic performance, and all must be present in such a manner that they are systematically and idiosyncratically functional. (Contains 5 figures and 4 tables.)