OBJECTIVE: This study assesses anonymous patient-level data on the use of sub-epidermal moisture (SEM) assessment technology as a tool in the prevention of pressure ulceration in at-risk hospital patients. METHOD: The relationship between technology-generated prompts for clinical action (patient turning, application of pressure redistributing equipment, heel protection or cream) and consequent clinical action was evaluated using data cross-tabulations (using data aggregated over multiple anatomical sites); in a multilevel model with patients clustered within wards, clustered in turn within hospitals, and controlling for additional patient- and institution-level factors; and using receiver operating characteristic (ROC) analyses of anatomy-specific data. The ability of the SEM assessment technology to detect deep and early-stage pressure ulcers/injuries on specific anatomical areas of a patient's body on admission, earlier than visual and tactile skin tissue assessments (STA), was assessed. RESULTS: A total of 15,574 patient assessments ('cases') were reported on 1995 patients. Most incidences of nurse action were in response to a prompt from SEM assessments (4944/5494; 90.0%). An SEM delta (Δ)≥0.6 resulted in nurse action in 4944/13,071 cases (37.8%). The multilevel model revealed strong evidence that SEM Δ prompts were significantly associated with nurse action (p<0.001; adjusted odds ratio: 1.99). CONCLUSION: In this study, SEM assessment technology effectively prompted nurse action moreso than skin reddening diagnosed via trained clinician judgement and STAs. While baseline responses of nurses' actions remained low, with or without SEM Δ prompts, findings verified the 'clinical utility' of SEM assessment technology as an objective prompt for early clinical action over and above existing mechanisms.