Pesticides are the best examples of risky compounds because they spread all over the environment. The experiments were performed to determine the effect of the Stomp 330EC herbicide at concentrations of 0.5 x 103, 1 x 103, 2 x 103 and respectively 4 x10 3 ml of herbicide/l of water on Pelophylax ridibundus tadpoles and adults. The herbicide produces delay and reduction of hatching (at the concentration of 0.004 ml/l), slowing of growth in volume and length as well as decreased oxygen consumption and survival of the tadpoles. The frequency of buco-pharingeal movements in adults of marsh frog is influenced by the Stomp® 330 EC herbicide at a concentration of 0.002 and 0.004 ml/l of water. After 14 days of exposure to the herbicide, the average number of erythrocytes increases, the average number of leukocytes decreases and the level of glucose changes.