The haematology of Tilapia sparrmanii (Smith) was investigated after exposure to 0.098 mg.l-1 hexavalent chromium at three different pH values. 2. Statistically significant changes occurred between the values of parameters of experimental and control fish. 3. At lower pH values erythrocytosis and leucocytosis were evident. 4. At an alkaline (9) pH anaemic and leucopenic conditions were observed. 5. T. sparrmanii adapted to chronic exposure to hexavalent chromium.