An in situ oil shale process water (Omega-9 water) was used in sublethal concentrations in flow-through bioassay with rainbow trout (Salmo gairdneri). Exposure for 96 hr to 0.3% of Omega-9 water (approximately 70% of the LC50) decreased blood packed cell volume (PCV) and HB concentration. This concentration of Omega-9 water also decreased plasma alkaline phosphatase (AP) activity and protein concentration and caused 3-fold increases in plasma NH/sub 3/ 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 NH/sub 3/ levels. No sublethal effects on blood HB, protein, and alkaline phosphatase occurred at a toxic level <1/5 of the level of the LC50.