Background: delirium is a common condition associated with poor outcome among older people. Despite its common occurrence, the pathophysiology of delirium remains poorly understood. Objective: to investigate the relationship between levels of cytokines, including monocyte chemoattractant protein (MCP-1), C-reactive protein (CRP), tumor necrosis factor-alpha (TNFa), interleukin-6 (IL-6), interleukin-10 (IL-10), and insulin-like growth factor 1 (IGF-1), and the development of delirium in a sample of hip fracture patients. Design: prospective study conducted on hip fracture patients. Measures: patients were screened for delirium on a daily basis using the Confusion Assessment Method (CAM). Levels of cytokines were measured at time of arrival, and, if possible, also postoperatively. Results: 19 patients were included in the study, median age was 83 years. 12 of the patients were screened for delirium preoperatively. Levels of IGF-1 measured preoperatively were statistically significantly lower in patients with preoperative delirium (n=5) compared to patients without preoperative delirium (n=7) (median 40.0 ng/ml vs. 75.0 ng/ml, p=0.04). From 13 patients blood samples were also collected postoperatively. Among these, the number of patients with a raise in MCP-1 was statistically significantly higher in the group with delirium in the postoperative phase compared to the no-delirium group (5/6 vs. 1/7, p=.03). Conclusions: patients with preoperative delirium had lower levels of IGF-1, whereas delirium in the postoperative phase was associated with a raise in MCP-1. Our results indicate that the inflammatory response might be of importance in the development of delirium.