A laboratory population of fourth-instar larval forms of Chironomus attenuatus Walker received a continuous life-long exposure of 0, 3, 8, 11, 16 and 22 ppm phenol. Water temperature, pH and dissolved oxygen concentration were monitored. Exposed larvae were analyzed for oven-dry weight, ash-free weight, caloric content, and oxygen uptake. Caloric content per gram in larvae increased with increasing phenol content up to a maximum of 5,869 cal/g in larvae exposed to 16 ppm phenols. Linear equations were formulated to relate energy content to phenol level and energy content and distance downstream from an outfall. Larvae were also exposed to 6 different salt concentrations between 0 and 342 mM/l for 4 different time periods. Concentration of sodium in the haemolymph was similar in larvae exposed to the lower concentrations and increased progressively at the three higher concentrations, while chloride levels increased steadily with increasing salt concentration.