The paper presents a simple theory for predicting seizure times for journal bearings. Under conditions of insufficient lubrication when bearing friction is high, seizure is predicted to occur in less than 20 seconds of operation. Insufficient lubrication can occur during bearing start-up, application of unusual loads, or as a result of an interruption of the lubricant supply system. Three examples where bearing seizure has been observed are discussed and the actual times to seize are compared with theoretical predictions. The actual seizure times are slightly less than predicted by theory, which is probably the result of bearing imperfections or uneven loading not considered in the theory.