After startup, fluid film bearings for hydroelectric units are designed to operate within nearly steady temperature ranges. Deviations from steady temperatures, especially during steady operating conditions, can be a sign of abnormal conditions or bearing surface damage. This presentation covers two aspects of abnormal conditions. First, during the startup, a significant thermal transient may occur. This thermal transient, if starting from low temperatures, can contribute or cause a loss of clearance during startup which results in significant damage to guide and journal bearings. Second, heavily loaded bearings, notably the thrust bearing in vertical hydroelectric units must maintain operating conditions sufficient to sustain an adequate hydrodynamic film during steady-state, full-load operation. Depending on the thrust bearing configuration, different design features are implemented to limit the peak lubricant temperatures in the bearing. The presentation concludes with some recommendations on the use of temperature monitoring to detect operating temperatures which indicate potential, or evolving, damage.