There is a paucity of data, and no consensus, about the composition of interdisciplinary teams of healthcare worker (HCW) that provide care in intensive care units (ICU). Delineate the nature and variation of HCW staff composition in US adult ICUs before the COVID-19 pandemic. A national survey of 574 adult ICUs inquired about ICU staffing. Two sets of survey items asked about: (a) "availability to provide care" in ICU for 11 HCW types, collapsed into six groupings, and (b) presence in formal ICU clinical rounds of nine HCW types, collapsed into six groupings; bedside nurses were assumed to be involved in both categories. Analysis was descriptive, seeking to examine the predominant and full range of staffing patterns. Of surveyed ICUs: 94% were in metropolitan areas, 63% in teaching hospitals, 74% had >250 beds, 66% cared for mixed adult patient types (e.g. medical-surgical), median ICU bed count was 20 (interquartile range 12-25), 27% used some form of telemedicine. In addition to bedside nurses, the core staffing group comprised intensivists, respiratory therapists and pharmacists; in 88% of ICUs all were available to provide care. However, there were 28 different combinations of the six groupings (intensivists, respiratory therapists, pharmacists, attending physician support, advanced bedside nurse support, nurse aides), with the most common one, present in 38% of ICUs, including all six. 96% of ICUs had interprofessional rounds at least five days a week; 78% had them on weekends. Among the ICUs with rounds, 61% of weekday rounding teams included all of intensivists, respiratory therapists and pharmacists. Nutrition, rehabilitation and social support practitioners each participated in rounds in 35-80% of ICUs, and altogether in 28% of ICUs. Except for intensivists, all HCW types participated much less commonly in weekend than in weekday rounds. ICU care almost always included a core team of bedside nurses, intensivists, respiratory therapists, and pharmacists. Beyond that core, great variability was seen in the presence of many other HCW types. Almost all ICUs had interprofessional rounds, with three-quarters also having them on weekends.