Introduction: The “golden hour” is the concept that timely assessment and resuscitation can improve outcomes in the critically ill. These principles are well-established in trauma patients, and rapid administration of evidence-based interventions has also been shown to improve outcomes in patients with sepsis. The best approach to perform this rapid evaluation and treatment, however, has not been previously evaluated in the ICU. Our aims are to observe common approaches to the assessment of critically ill patients upon ICU admission, to compare them to the established Checklist for Early Recognition and Treatment of Acute Illness and iNjury (CERTAIN) that has been associated with improved patient outcomes, and to examine the impact of observed variations in practice. Methods: We conducted a prospective observational study in Mayo Clinic ICUs. We recorded ICU team actions during patient admissions, including performance of primary assessment, vital signs, IV access confirmation, labs and ultrasound, differential diagnosis, and plan by systems, including code status. Data were analyzed to identify practice patterns, assessment gaps, and length of stay. Results: Data on 16 MICU patient observations has been analyzed to date. The patient median age was 65.5 years, 40% were female, and the mean ICU length of stay was 2.7 days. Recorded frequency of airway assessment was 73%, breathing 73%, circulation 93%, disability 33%, and exposure 80%. 73% of patients had their vital signs evaluated, and 60 % had IV/IO access obtained. 62% had cardiac POCUS, while only 31% had lung ultrasound and 25% had an abdominal ultrasound. The most frequently addressed systems during the discussion of plans were cardiovascular and pulmonary at 62% and 75%, with neurologic and hematologic discussed in 25%. The least commonly discussed system was endocrine (12.5%). Nurses completed 36% of admission tasks, while 50% of plan by system tasks were completed by residents. Conclusions: We describe variations in assessment during admission. Gaps in assessment are frequently observed during the golden hour compared to the CERTAIN checklist, arguing that a systematic approach is necessary to avoid errors of omission. Additional research is needed to determine the impact of these variations in practice on ICU patient outcomes.