To assess the management of diabetic ketoacidosis (DKA) and evaluate if introduction of a critical pathway improves management, we studied adults admitted with DKA to the Medicine and Critical Care Services in a US teaching hospital. Patients admitted with DKA in 1997 before implementation of the critical pathway were the control group (n=72). In 1998, housestaff and nurses in the emergency department (ED) and on the General Medicine and Critical Care Services were instructed in the use of the critical pathway. Patients admitted with DKA during 1998 (n=77) were the intervention group. Length of stay (LOS), hospital cost, adherence to guidelines, and medical outcomes to be avoided were compared, and regression analyses were performed to correlate processes and outcomes of care. Mean LOS and variability in LOS decreased during the intervention period, especially in patients treated without endocrinology consultation (EC) (5.2 +/- 10.6 vs. 2.4 +/- 2.1 days, P=0.01), and hospital cost and variability in cost tended to decrease ($6441 +/- 15,204 vs. $3625 +/- 3478, P=0.24). More intervention subjects received the recommended intravenous fluid volume (88 vs. 71%, P=0.013), education in sick-day management (77 vs. 54%, P=0.006), and EC (38 vs. 21%, P=0.03). Insulin management was not changed. We conclude that implementation of a DKA critical pathway reduced practice variation and was associated with shorter LOS and a trend toward decreased cost. Some processes of care were improved but many require additional interventions.