An in situ oil shale process water, designated Omega-9 water, was used in sublethal concentrations in flow-through bioassays with rainbow trout. Exposure for 96 hr to 0.3% of Omega-9 water (approximately 70% of the LC50) decreased blood packed cell volume (PCV) and hemoglobin concentration. This concentration of Omega-9 water also decreased plasma alkaline phosphatase (AP) activity and protein concentration and caused threefold increases in plasma ammonia levels. Exposure to sublethal concentration of a solution of the 13 major inorganic constituents of Omega-9 water also decreased PCV and plasma AP activity and increased plasma ammonia levels. This study also found that no sublethal effects on blood hemoglobin, protein and alkaline phosphatase occurred at a toxic level less than a fifth of the level of the LC50.