The 48-h acute toxicity range of nitrite to narrow-clawed crayfish, Astacus leptodactylus was within 22 and 70 mg L-1 (mean 29.43 mg L-1). Environmental chloride (100 mg L-1 chloride) increased the 48-h toxicity of nitrite to a range of 31 and 80 mg L-1 (mean 49.20 mg L-1). Hemolymph nitrite, total hemocyte counts (THCs), and hemolymph glucose were examined in A. leptodactylus exposed to different sublethal nitrite concentrations. The same parameters were also determined for A. leptodactylus exposed to different sublethal nitrite concentrations with additional environmental chloride. Additionally, hemolymph nitrite and THCs were analyzed for crayfish exposed to nitrite-free water after 24 h following a 48-h exposure to nitrite. In the nitrite-exposed tests, hemolymph nitrite increased directly with water nitrite; however, after recovery, nitrite in hemolymph decreased. In the nitrite plus chloride-exposed tests, the accumulation of nitrite in hemolymph was relatively low compared to the nitrite-exposed tests. Thus, hemolymph to environment ratios of nitrite in the nitrite-exposed tests were higher than those of nitrite plus chloride-exposed tests. THCs decreased following nitrite exposure and, in general, increased after recovery. In the nitrite with chloride exposed and recovery from nitrite tests, THCs increased. Hemolymph glucose levels elevated following nitrite exposure, independent of water nitrite concentrations. However, with environmental chloride nitrite exposure did not cause elevation of hemolymph glucose. Hemolymph nitrite accumulation was found to be closely related to the decrease in THCs and increase in hemolymph glucose. (C) 2003 Elsevier Inc. All rights reserved.