The results of a NIOSH investigation at a portland cement manufacturing plant (SIC-3241), carried out at the request of the local labor union and in accordance with the Health Hazard Evaluation (HHE) program, were reported. The HHE request pertained to the water blasting of the preheat tower, carried out by two kiln assistants on each of four rotating shifts. A total of 34 wet bulb globe temperature (WBGT) measurements were taken near each worker while operating the blasting gun. For Shift 1, time weighted average (TWA) for the duration of the operation was 88.5 degrees-F, for Shift 2 it was 90.5 degrees-F. Both values exceeded NIOSH Recommended Exposure Limits. A number of exposures during which the NIOSH ceiling limit of 97 degrees-F was exceeded, were also recorded. Furthermore, alternate workers were used who were not acclimatized. NIOSH WBGT Recommended Alert Limit and ACGIH WBGTTLV reductions for unacclimated water blasters and those wearing protective equipment were discussed. Body weight reductions up to 4 pounds with a mean of 2 pounds were observed. The authors conclude that these workers are subject to severe heat strain during water blasting. Recommendations pertain to engineering and administrative controls including medical evaluations, access to drinking water, and use of personal protective equipment.