Much is known about sport officials' decisions (e.g., anticipation, visual search, and prior experience). Comprehension of the entire decision process, however, requires an ecologically valid examination. To address this, we implemented a 2-part study using an expertise paradigm with ice hockey referees. Purpose: Study 1 explored the strategies referees indicated they used to make decisions. For Study 2, we sought to confirm the emergent codes of Study 1 and further examine referee expertise and evaluations of decision making. Method: In Study 1, 2 elite, 2 intermediate, and 2 novice referees wore helmet cameras for 1 game and participated in stimulated recall interviews, which were coded using theoretical and focused codes. Study 2 involved focus groups that each watched and commented on 2 helmet camera videotapes from Study 1; 1 videotape consisted of an elite referee's game and the other included an intermediate referee's game. The focus-group data were analyzed using the same coding structure from Study 1. Results: Combined, 3 distinct theoretical codes were identified: (a) primary referee strategies, (b) secondary referee strategies, and (c) cognitive and situational influences on refereeing. Study 1 showed that elite referees demonstrated more sophisticated knowledge of the 3 theoretical codes. In Study 2, elite referees demonstrated enhanced declarative knowledge compared with intermediate and novice participants. Conclusions: Elite referees have more elaborate knowledge bases than do nonelite referees. In the discussion, we explain our results and link them with the action plan profiles framework.