In the context of critical illness, hypotension may be associated with acute kidney injury (AKI). Using the MIMIC II database, we studied the risk of AKI in ICU patients as a function of both the severity and duration of hypotension. Multivariate logistical regression was performed to find correlations between hypotension and AKI. Minimum mean arterial blood pressure (MAP) and the amount of time MAP was below a range of hypotension thresholds in a target 48-hour window (prior to AKI onset) were used as primary predictive variables in the multivariate model. Our results indicate that the risk of AKI was related to the severity of hypotension with an odds ratio (OR) of 1.03, 95% CI 1.02-1.04 (p < 0.0001) per 1 mmHg decrease in minimum MAP ≥ 80 mmHg. For each additional hour MAP was less than 70, 60, 50 mmHg, the risk of AKI increased by 2% (OR 1.02, 95% CI 1.00-1.03, p = 0.0034), 5% (OR 1.05, 95% CI 1.02-1.08, p = 0.0028), and 22% (OR 1.22, 95% CI 1.04-1.43, p = 0.0122) respectively.