To the Editor.—The article by Zulick et al1 in the November 1991 issue of the Archives contained several erroneous assumptions and methodologic ambiguities that are of concern. First, the authors misrepresented the character and composition of hospitals contributing data to the Major Trauma Outcome Study (MTOS). These hospitals are not all "large, urban, level 1, state-of-the-art" trauma centers as stated. In actuality, the hospitals contributing data to the MTOS were predominantly "self-proclaimed" trauma centers. Few had verification by the American College of Surgeons or official designation by a state or regional agency. Among those participating, 64 hospitals were reported to be level 1, 40 were level 2, 11 were level 3, 17 were children's specialty centers, and there were seven hospitals whose level was not identified (some from the United Kingdom and Australia).2 The data were not stratified by hospital size, level, or geographic location. Hence, the