Although a positive FAST (focused assessment with sonography for trauma) examination in hypotensive blunt trauma patients generally suggests the need for emergent laparotomy, this finding's significance in normotensive trauma patients is unclear. We tested the association between a positive FAST and the need for therapeutic laparotomy in normotensive blunt trauma patients. This was a retrospective cohort analysis of consecutive normotensive blunt trauma patients presenting to two trauma centers. The outcome was therapeutic laparotomy. The unadjusted association between a positive FAST and laparotomy was odds ratio (OR) 116 (95% confidence interval [CI] 49.5-273). This association persisted after adjusting for confounding variables (OR 44.6, 95% CI 1.77-1124). Thirty-seven percent of patients with a positive FAST required therapeutic laparotomy vs. 0.5% with a negative FAST. Among normotensive blunt trauma patients, there was a strong association between a positive FAST and the need for therapeutic laparotomy. Very few normotensive patients with a negative FAST required therapeutic laparotomy.