Effluents from veterinary pharmaceutical industries that formulate medicines are mainly generated during the washing of equipment. The aim of this work was to evaluate the acute toxicity to Daphnia similis and chronic toxicity to Ceriodaphnia dubia of raw and treated effluents generated by a veterinary pharmaceutical industry. The industrial effluent treatment system comprises a step of chemical treatment (coagulation-sedimentation forced) followed by aerobic biological treatment (activated sludge process). Five samplings campaigns were performed from October 2011 to July 2012. The raw effluent samples showed high acute and chronic toxicity (acute: fourth sampling with EC50 - 48-h of <0.001% and chronic: third sampling with IC50 - 7-d of <0.0001%). The chemically treated effluent samples were the most toxic with EC50 - 48-h between <0.001 and 0.1% and IC50 - 7-d between 0.00001 and 0.0001%. This increase in toxicity is probably related to the use of aluminum sulfate as flocculating agent. The biological treatment led to a small reduction in toxicity of the effluents. The selected ecotoxicological tests were adequate for detecting the effluent toxicity and useful for evaluating the efficiency of the steps of the effluent treatment. Improvements in the industrial wastewater treatment system should be implemented in order to reduce the observed toxicity of the final effluent.82168179(2009) NBR 12.713: Ecotoxicologia aquática-toxicidade aguda-método de ensaio com Daphnia spp. (Cladocera, Crustacea)., p. 21. , ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Rio de Janeiro(2010) NBR 13373: Ecotoxicologia aquática-toxicidade crônica-método de ensaio com Ceriodaphnia spp. (Cladocera, Crustacea)., p. 15. , ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. 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