Adult grass shrimp (Palaemonetes pugio) were collected during July and August, 1973, and exposed for 48-hr periods to a series of sublethal cadmium (Cd) concentrations: 0.1 and 0.56 mg/l for metabolic studies; and 0.01, 0.05, 0.1, 0.3, 0.56 mg/l for locomotor studies. Treatment effects were tested singly and in combination at selected dissolved oxygen (DO) concentrations ranging from near saturation to 0.8 mg/l. Shrimp not exposed to Cd exhibited metabolic regulation between 6.5 and 4.6 mg DO/l, with progressively lower O2 consumption rates at lower DO concentrations. Oxygen consumption of Cd-exposed shrimp was suppressed overall relative to the non-Cd treated shrimp, and with one exception, the magnitude of metabolic suppression directly corresponded to Cd concentration. Locomotor activity of non-Cd exposed shrimp was relatively independent of DO concentration down to 2.8mg DO/l and became significantly suppressed at 1.8mg DO/l and below. (Copyright (c) Springer-Verlag 1985.)