The effect o f corn-cob controlled-release formulations (CRF) o f thiobencarb (TA I and TA2) and alginate CRF (TAL 70192) to the freshwater shrimp, Macrobrachium lanchesteri (D e M an), in comparison to a conventional granular formulation was studied in the laboratory. Mortality o f the shrimps 24 h after exposure to the conventional formulation was significantly higher (P < 0 .0 5), and increased to 93.3% after 120 h. The CRF of TA1, TA2 and TAL 70192 caused mortality o f 19.2, 5.8 and 8 .5%, respectively, 120 h after exposure. This difference is due to the slower release o f thiobencarb using CRF.