Investigation of the clinical signs of acute oral intoxication by diquat (Verbetskii & Pushkar, 1968; Clark & Hurst, 1970; Crabtree et al., 1977; Cobb & Grimshaw, 1979) have established gastrointestinal disturbance as the major syndrome of poisoning and as a cause of death. In both rats and guinea-pigs, the clinical signs of acute oral poisoning (Verbetskii & Pushkar, 1968) were dose-dependent. At doses greater than the LD50, signs of poisoning appeared after 6 - 12 h; at lower levels, the signs were less obvious and appeared after 1 - 2 days. Most deaths occurred on the 3rd - 9th day after oral administration.